Parenting interventions to support parent/child attachment and psychosocial adjustment in foster and adoptive parents and children: A systematic review

Parenting interventions support the overall psychosocial adjustment of children in foster and adoptive families

The problem, condition, or issue

Every day, foster and adoptive parents around the globe care for children who have experienced serious adversity at a young age. From 2004 to 2010, between 29,000 and 45,000 children were internationally adopted each year (Selman, 2012). Globally, the number of inter country adoptions is declining, and in 2013 there were three times fewer international adoptions worldwide than in 2003 (Mignot, 2015). However, domestic adoption out-number inter country adoption by far. Thus, the UN estimates that around 260,000 domestic adoptions take place worldwide each year.

Adopted children and children placed in foster care are at increased risk of developing a range of mental health, behavioural, and psychosocial adjustment problems (Bimmel et al., 2003; Brand & Brinich, 1999; Oswald et al., 2010; Pears & Fisher, 2005; Pecora et al., 2009). In a meta-analysis based on 25,281 adoptees and 80,260 controls, adopted children showed more behaviour problems (effect sizes ranged between d 0.16–0.24) and were much more likely to be referred for mental health services than their nonadopted peers (d, 0.72). Furthermore, domestic adoptees showed more behaviour problems and were more likely to be referred for mental health services than international adoptees (Juffer & van IJzendoorn, 2005).

Foster children are also much more likely to experience behaviour and mental health problems than children living with their family of origin. Research on children placed in out-of-home care in the United States suggests that between 23% and 61% of children under the age of 5 are significantly delayed when screened for developmental problems (Stahmer et al., 2005). Similarly, a study based on 267 children in foster care aged 0–17 years found the rate of behavioural problems in the clinical range to be two and a half time the expected rate in a comparable community sample (Clausen et al., 1998). Finally, a recent study by Turney and Wildeman (2016) based on data from the 2011–2012 US National Survey of Children's Health compared parent-reported mental and physical health outcomes of children placed in foster care to outcomes of children not placed in foster care. In this study, Turney and Wildeman (2016) conclude that children in foster care are in poor mental and physical health relative to children in the general population. Thus, children placed in foster care were twice as likely to have learning disabilities, developmental delays, and speech problems. Furthermore, children placed in foster care were three times as likely to have ADD/ADHD, five times as likely to have anxiety, six times as likely to have behavioural problems, and seven times as likely to have depression (Turney & Wildeman, 2016). When studying the health of foster children it should, however, be noted, that there may potentially be discrepancies between countries due to differences in child protection legislature regulating at what point children are placed in foster care. Placing a child in foster care may be considered an intervention in itself, however, a recent meta-analysis based on longitudinal studies of foster children showed that foster care does neither negatively nor positively influence the developmental trajectories of foster children, meaning that the mental health and behaviour problems in foster children when they entered foster care were unlikely to decrease over time (Goemans et al., 2015). With regard to adopted children, longitudinal studies suggest a complex pattern of both vulnerability and catch-up, in which adopted children come to resemble their none-adopted peers. In a consensus statement, researchers from different disciplines suggest that while there are significant benefits of adoption compared to remaining in vulnerable families or institutional care, adopted children are more vulnerable than none-adopted children and some problems are likely to to persist post adoption (Palacios, Adroher et al., 2019). This evidence points to the need for interventions to support children in both foster and adoptive families.

Mental health issues and behaviour problems in foster and adopted children are often further exacerbated in the detrimental event of a placement breakdown (Goemans et al., 2015). Within research on adoption and foster care placement, different terminology has been employed to describe placement disruptions and breakdown. In this review we use the term placement breakdown broadly to refer to the situation in which a foster or adopted child is either temporarily or permanently physically separated from the foster or adoptive parents regardless of the legal status. That is, whether the adoption process was finalised or not and whether the legal parental rights are terminated or not (Palacios, Rolock, et al., 2019). Placement breakdown does, however, not refer to the situation in which a foster child is returned to the biological parents due to improvements in the parenting ability or the life circumstances of the biological parents. Nonetheless, an incidence of placement breakdown is difficult to estimate precisely due to variation in terminology, research designs, measurement, and available statistics. In a recent review of the existing literature on adoption breakdown and disruption, Palacios, Adroher, et al. (2019) report incidence rates ranging from just 1%–23% in different studies. The study with the lowest incidence only measured disruptions or breakdown occurring in the timeframe when the adoption paper work was still being processed, which is not when most disruptions or breakdowns happen. In comparison, the study with the highest incidence was based on a population of children adopted at age 5–11 years. Age at adoption is known to be associated with placement breakdown, with older children being more at risk. These findings illustrate why the exact extend of the problem with adoption placement breakdown cannot be determined globally at this point. Similarly, it is estimated that between 20% and 50% of children in long term foster care will experience that their planned stay in their foster family ends prematurely (Oosterman et al., 2007). Regardless of the exact extend of the problem with placement breakdown, it is clear that it constitutes a serious risk, as placement breakdowns are both costly to the society and can have devastating consequences for vulnerable children (Newton et al., 2000; Palacios, Adroher, et al., 2019; Strijker et al., 2008).

To understand the aetiology of the problems experienced by foster and adoptive families and children, it has been suggested that the attachment relationship between the child and the adoptive/foster parents may become a source of psychological vulnerability. Bowlby's (1969) theory of attachment states that parent/child care giving is a goal-directed behavioural system accompanied by strong motivational effects and shaped by the adaptive function of protecting the offspring. Thus, through the child's interactions with the primary caregiver and based on the caregivers' responses to the child's need of “a secure base,” inner working models of attachment are established early in life. Developing a secure attachment relationship with a parent or primary caregiver has long-term benefits for children because of the impact on children's later adaptation and socioemotional development and thus a secure attachment style may be seen as a source of psychological resiliency (Cassidy & Shaver, 2002). Ainsworth et al. (1971, 1974) and Main and Solomon (1990) developed a typology of attachment patterns in children, which can be assessed and classified based on the child's behaviour in a laboratory exploration known as the Strange Situation Procedure. In children, attachment classification includes three categories describing organised attachment patterns; Secure, Insecure-avoidant and Insecure-resistant, as well as a fourth category known as disorganised-disoriented, which may be superimposed on the existing categorisation in cases where the child exhibits behaviours characterised by breakdowns of the organised attachment pattern. Securely attached children develop basic trust in self and others, enabling them to function autonomously. In the Strange Situation Procedure securely attached toddlers are able to cope with a short separation from the caregiver and are easily comforted upon the return of the caregiver. In different ways, toddlers with insecure-avoidant or insecure-resistant attachment styles are less able to cope with the short separation from their primary caregiver, and they are not as easily comforted upon the return of their caregiver as the securely attached toddlers are. Some attachment scholars have proposed that toddlers in the avoidant category are frightened of appearing vulnerable. Thus, they may ignore their caregiver whilst still showing elevated signs of physiological arousal, indicating high levels of stress in response to the separation. Toddlers in the resistant category are hypothesised to perceive care giving as unpredictable and thus may show a behaviour characterised by ambivalence towards the caregiver, such as excessive crying when the caregiver leaves and an inability of be comforted upon the return (Ainsworth et al., 1978). The Disorganised-disoriented attachment category was added to the theory based on observations of children who did not seem to fit the description of the original patterns. Main and Solomon (1990) proposed that this category was characterised by breakdowns of attachment organisation following trauma. A number of studies support the associations between disorganised-disoriented attachment in early childhood and the subsequent development of adverse child outcome (Alpern & Repacholi, 1993; Carlson, 1998; Groh et al., 2014; Moss et al., 2006).

Adopted children and children placed in foster care share experiences of early separation from caregivers, leaving them at elevated risk for developing insecure and/or disorganised-disoriented attachment. In a series of meta-analyses based on 39 studies (N = 2912 adopted children) Van den Dries et al. (2009) found that children, who were adopted after their first birthday, showed less attachment security than their nonadopted peers did. This was similar to the attachment distributions in samples of children in foster care. Furthermore, Van de Dries et al. (2009) concluded that adopted children, regardless of age at the adoption and similarly to foster children, showed more disorganised attachment compared to their nonadopted peers (Van den Dries et al., 2009).

Description of the intervention

How the intervention might work

Although the capacity for developmental change diminishes with age, change continues throughout the life cycle so that changes for better or for worse are always possible. It is this continuing potential for change that means that at no time of life is a person invulnerable to every possible adversity and also at no time of life is a person impermeable to favourable influence. It is this persisting potential for change that gives opportunity for effective therapy (Bowlby, 1988, p. 154).

By definition, foster and adopted children have experienced a separation from their biological parents. Furthermore, foster and adopted children have often experienced adverse events such as insufficient medical care, malnutrition, physical and emotional abuse, and neglect before their initial placement (Sullivan & van Zyl, 2008). Thus, the children may be physically and psychologically vulnerable at the time of the placement and this vulnerability may continue to manifest itself throughout their life course in various ways (Palacios, Rolock, et al., 2019). However, as proposed by Bowlby within the above quotation, attachment is a dynamic phenomenon, and there is continuous potential for positive changes through the child's interactions with sensitive caregivers. This potential is what attachment interventions are aimed at supporting. According to Bowlby (1988), a child will experience grief, anger and distress as a result of temporary or permanent loss of access to existing attachment figures, and this can only be resolved if the child is able to develop new attachment relationships with alternative caregivers. By supporting a child's current caregivers (e.g., the foster or adoptive parents) in meeting the needs of the child in a consistent and sensitive manner, attachment-based interventions are proposed to be able to change the child's internal working models of attachment, leading to an increased sense of “felt security.” Attachment-based interventions are thus designed to help foster and adoptive parents to notice and understanding subtle and overt emotional cues in their child's behaviour and to respond to these cues in a sensitive, contingent, and consistent manner. Sometimes this process may involve a reflection on the attachment history and the current “states of mind” with respect to attachment of the adoptive or foster parents themselves (Juffer et al., 2008). The reason for the assumed benefits of working with the caregiver's own state of mind with respect to attachment is that this has been identified as the strongest predictor of whether foster children will become securely attached to a foster parent or not (Dozier et al., 2001). However, in a study comparing VIPP and VIPP-R with a control condition in a sample consisting of mothers with <14 years of education, who were classified as insecure and their first born infants, Veldenman et al. (2006) found overall differences between the two intervention groups and the control group on measures of maternal sensitivity postintervention, but no significant differences were found between the two interventions, suggesting no added benefits of working with maternal attachment representations compared to the VIPP intervention alone.

Typically, attachment-based interventions consist of sessions in which the therapist is working with the parent(s) and children simultaneously. In subsequent sessions the parents are provided with feedback, education about attachment, and are invited to reflect upon their experiences with the child.

Why it is important to do this review

Based on findings on the associations between early disorganised-disoriented attachment and subsequent adverse child outcomes, a number of interventions and programmes are aimed at supporting the development of a secure attachment relationship between parents and children (Dozier & Rutter, 2008; Dozier et al., 2001). In a meta-analysis on the effectiveness of preventative attachment interventions on parental sensitivity and infant attachment for at risk populations 70 studies were traced, producing 88 intervention effects on sensitivity (n = 7636) and/or attachment (n = 1503). Randomised interventions appeared rather effective in changing insensitive parenting (d = 0.33) and infant attachment insecurity (d = 0.20) (Bakermans-Kranenburg et al., 2003). In a systematic review co-registered at Cohrane and Campbell, Barlow et al. (2015) explored the efficacy of attachment-based parent-infant psychotherapy on parental and infant mental health. This review focused on infants aged 0–24 months within vulnerable families (defined as families in which parents were suffering from mental health issues, drug/alcohol abuse, or were victims of domestic violence). Findings from this review suggest that parent-infant psychotherapy is a promising approach in terms of improving infant attachment security in high-risk families. However, there were no significant differences compared with no treatment or treatment-as-usual for other parent-based or relationship-based outcomes, and no evidence that parent-infant psychotherapy is more effective than other ways of working with parents and infants. The review by Barlow and colleagues provides important insight into the efficacy of attachment-based interventions, however, the findings may not be applicable to the population of the present review for two main reasons. First, the population of adoptive and foster parents are typically resourceful individuals highly motivated for participation in interventions. Second, Barlow et al. (2015) focused only on therapeutic interventions that could be described as parent-child psychotherapy and only included infants under the age of 2 years. Juffer et al. (2017) provides a review and meta-analysis of the effectiveness of Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline (VIPP-SD), which is an intervention based partially on attachment theory with various populations of at-risk parents and vulnerable children (k = 12). In the review positive effects of VIPP-SD were found on measures of sensitive parenting and socio-emotional child outcomes.

Kerr and Cossar (2014) conducted a systematic review of studies of attachment-based interventions with foster and adoptive parents and children aged 0–17 years. This narrative review provides preliminary insights and suggests that there are positive effects of attachment-based interventions for this population, but it lacks the methodological rigour of a Campbell review and needs to be up-dated. Furthermore, the review by Kerr and Cossar (2014) only provides a very limited description of the quality appraisal process and it does not include meta-analysis. Thus, the efficacy of attachmentbased interventions on measures of both attachment security and on measures of parent/child psychosocial adjustment in foster and adoptive families is yet to be thoroughly examined, which is where the present review will contribute.

Finally, a recent meta-analytic review (k = 53) examined the effects of all types of parenting interventions in foster care and adoption on eight types of outcomes (Schoemaker et al., 2019). Results show positive effects on four parenting outcomes (sensitive parenting, dysfunctional discipline, parenting knowledge and attitudes and parenting stress, and on one child outcome (behaviour problems), whereas the review did not find effects for attachment security, child diurnal cortisol levels or placement disruptions. This review provides many insights, however the present review will provide an extensive risk of bias analysis of each included study, update the searches and focus exclusively on the specific effectiveness of attachment-based interventions.

The Hague Convention of May 29, 1993 on Protection of Children and Co-operation in Respect of Intercountry Adoption (Hague Adoption Convention) requires all signatory states to: “promote the development of adoption counselling and post-adoption services in their States” (article 9). In Denmark, this has resulted in the 2016 establishment of national post-adoption services providing all adoptive parents with postadoption family counselling. The present review provides knowledge of the efficacy of a range of interventions commonly offered to adoptive parents. Furthermore, the present review is relevant for child protection agencies across the world with the authority to place children in foster care.

Criteria for considering studies for this review

Search methods for identification of studies

We implemented a wide range of search methods and strategies to maximise coverage of relevant references, while simultaneously attempting to reduce different types of bias related to publication and dissemination systems. The different strategies and methods will be presented below.

Data collection and analysis

Description of studies

Results of the search

The results of the search are summarised in Figure 1. The total number of potential relevant records was 17,822 after excluding duplicates (database: 22,286 grey, hand search, snowballing and other resources: 4365). All records were screened based on title and abstract; 17,396 were excluded for not fulfilling the screening criteria, 21 records were unobtainable despite efforts to locate them through libraries and searches on the Internet and 426 records were ordered, retrieved and screened in full text. Of these, 381 did not fulfil the screening criteria and were excluded. Seven studies were excluded at a later stage, with reasons specified in the appendices under Characteristics of excluded studies. A total of 44 studies were included in the review. The references are listed in section References to included studies.

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Figure 1

Study flow diagram

Risk of bias in included studies

The risk of bias coding was carried out in accordance with the protocol (Dalgaard et al., 2020) and the assessment of each of the 44 studies is available in a Supporting Information document. For a summary of the risk of bias assessments, see Tables 5 and 6.

Thirty-five studies reported the results of 19 RCTs. Of the RCT's three had a published a priori protocol or a priori analysis plan. Seven studies used nonrandomised designs and two studies reporting on the same trial used a mixture of randomisation and matching and was assessed as a nonrandomised study. None of the nonrandomised studies had an a priori protocol or an a priori analysis plan.

A total of 15 studies (six nonrandomised and nine randomised) were assessed as having an overall critical risk of bias, corresponding to a risk of bias so high that we decided not to use the studies in the data synthesis. Of these studies, five nonrandomised studies had a critical risk of confounding bias (and some of these on other risk of bias domains as well), and one nonrandomised study was rated overall Critical due to multiple ratings of Serious risk of bias on other domains. The main reason for rating them Critical risk of bias was that they failed to establish a comparison group that was balanced on important confounders and in addition, no confounders were controlled for.

Of the nine studies reporting on RCTs (five trials) and rated Critical risk of bias overall, two were rated Critical risk of bias on the Randomisation process domain (and one of them on the Deviation bias domain as well); in one study due to a high degree of self-selection into groups despite randomised assignment of participants and in addition large pre test imbalances between groups and in the other study due to randomisation before recruitment and consent of participants, and a large part of the recruited either did not meet study criteria or declined participation and it was not possible to assess baseline imbalances.

One study was rated Critical risk of bias on the Deviation bias domain; this study was a follow up study to a trial where a wait list design was used and the study analysed a 12 months follow up outcome at a time point where those participants in the control group interested had taken up the intervention. Six studies (reporting on two trials) were rated Critical risk of bias on the Reporting bias domain. Five of these studies reported on a trial which in general was very badly reported, only the results of selected sub groups of participants as well as outcomes were reported. The last study was a very selectively reported follow up study to a trial otherwise used in the data synthesis.

As described in the protocol, we stopped the risk of bias assessment, when a study was given a judgement of “Critical risk of bias” in one domain.

No study had an overall low risk of bias. As it is not possible to blind participants or the provider of the intervention in these kinds of studies, it is not possible for a study to achieve a low risk of bias. The highest overall rating a study can acquire is Some concerns, which was aquired by 23 RCT studies.

Three nonrandomised studies had an overall rating of Serious risk of bias, and four had an overall rating of High risk of bias.

In two RCT studies, the overall risk of bias were rated differently for the reported outcomes, in these cases, the summary risk of bias scores are based on the outcomes with the most favourable rating. In N´zi Amanda et al. (2016) one outcome (Dyadic Parent-Child Interaction Coding System) was judged to have an overall High risk of bias, whereas the remaining outcomes were judged to have an overall rating of Some concerns. In Lind et al. (2020) one outcome (child observed social-emotional competence) was judged to have an overall High risk of bias, whereas the other outcomes were only judged to have Some concerns.

The majority of RCT studies, 24 studies, were rated Some concerns on the randomisation process (only assessed for the RCT studies), five were rated Low risk of bias, two were rated High risk of bias, two were rated Critical risk of bias and for the remaining two there were either no information (rated Unclear) or the domain was not applicable (the study had a rating of Critical risk of bias on another domain).

On the three domains only assessed for the nonrandomised studies, four were rated Serious risk of bias on the Confounding domain and five were rated Critical risk of bias; three studies were rated Serious risk of bias on the Selection bias domain, one was rated Low risk of bias, two were rated Critical risk of bias and the domain was not applicable for the remaining nonrandomised studies; two studies were rated Serious risk of bias on the Classification domain, two were rated Low risk of bias and the domain was not applicable for the remaining nonrandomised studies.

On the remaining domains (common to RCTs and nonrandomised studies) no studies were rated Low risk of bias on the Deviation domain, the majority, 34 studies, were rated Moderate risk of bias/Some concerns, one study was rated Serious risk of bias, two were rated Critical risk of bias and the remaining studies were either unclear or not applicable in this domain. On the Missing data domain the majority were rated either Low risk of bias (13 studies) or Some concerns (18 studies), five were rated High/Serious risk of bias and the remaining studies were not applicable in this domain. On the Measurement bias domain most (25 studies) were rated Low risk of bias (one of these studies in addition reported an outcome that was rated Some concerns), 11 were rated Moderate risk of bias/Some concerns (one of these studies in addition reported an outcome that was rated High risk of bias) and the remaining studies were not applicable in this domain. Finally, on the Reporting bias domain three studies were rated Low risk of bias, the majority (24 studies) were rated Moderate risk of bias/Some concerns (one of these studies in addition reported an outcome that was rated High risk of bias), three were rated High risk of bias, six were rated Critical risk of bias and the remaining studies were not applicable in this domain.

Effects of interventions

Synthesis of results

The analyses presented in this section restrict attention to those studies that permitted extraction of an effect size, and were not rated Critical risk of bias (44 studies with data from 27 different samples).

All effect sizes were coded such that a larger effect size indicated better outcomes for the treated group (children or caregivers). Effect sizes that were derived from dichotomous measures were converted to a SMD using the methods outlined in section Methods. To carry out a meta-analysis, every study must have a comparable effect size. We synthesise effects separately by type of outcome (conceptual outcomes as outlined in section “Types of outcomes measures”) and time point (end of intervention and follow up).

Child outcomes at end of intervention

Overall psychosocial adjustment

Ten studies analysed the effect of attachment-based interventions on the overall psychosocial adjustment of foster or adopted children as reported by their caregivers post intervention. Measures used include the Child Behavior Checklist, The Strengths and Difficulties Questionnaire, BITSEA and Eyberg Child Behavior Inventory. Two of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group and statistically significant. The random effects weighted SMD is 0.37 (95% CI, 0.10–0.65). The forest plot is displayed in Figure 2. There is some heterogeneity between the studies; the estimated τ ² is 0.10, Q = 20.63, df = 9 and I ² is 56%.

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Figure 2

(Analysis 1.1) Child outcomes, overall psychosocial adjustment

Externalising behaviour problems

Eights studies analysed the effect of attachment-based interventions on the externalising behaviour problems of foster and adopted children using sub scales from the Child Behavior Checklist, The Strengths and Difficulties Questionnaire and BASC as reported by their caregivers post intervention. Two of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.37 (95% CI −0.09–0.83). The forest plot is displayed in Figure 3. There is a large degree of heterogeneity between the studies; the estimated τ ² is 0.33, Q = 37.69, df = 7 and I ² is 81%.

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Figure 3

(Analysis 1.2) Child outcomes, externalising behavior

Internalising symptoms

Five studies analysed the effect of attachment-based interventions on internalising symptoms of the foster and adopted children post intervention as reported by their caregivers. Measures include sub scales from the Child Behavior Checklist, The Strengths and Difficulties Questionnaire and the Anxiety sub scale from TSCYC. All the reported results indicate a positive effect and the weighted average is positive, favouring the treated group and statistically significant. The random effects weighted SMD is 0.20 (95% CI −0.02–0.42). The forest plot is displayed in Figure 4. There is no heterogeneity between the studies; the estimated τ ² is 0.00, Q = 1.03, df = 4 and I ² is 0%.

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Figure 4

(Analysis 1.3) Child outcomes, internalising symptoms

Observed child attachment security

Three studies analysed the effects of attachment-based interventions on the observed attachment security of foster and adopted children as measured by independent observation. Measures include the Strange Situation procedure, Attachment Q-Set and The Emotional Attachment & Emotional Availability Clinical Screener. All the reported results indicate a positive effect and the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.59 (95% CI, −0.40–1.57). The forest plot is displayed in Figure 5. There is some degree of heterogeneity between the studies; the estimated τ ² is 0.47, Q = 5.25, df = 2 and I ² is 62%.

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Figure 5

(Analysis 1.4) Child outcomes, observed attachment security

Observed positive child behaviour

Four studies analysed the effect of attachment-based interventions on positive child behaviour post intervention as measured by independent observation of video-taped interaction between the child and caregivers. Measures include DB-DOS and Emotional Availability Scales. All the reported results indicate a positive effect and the weighted average is positive, favouring the treated group and statistically significant The random effects weighted SMD is 0.39 (95% CI, 0.14–0.64). The forest plot is displayed in Figure 6. There is very little heterogeneity between the studies; the estimated τ ² is 0.01, Q = 3.36, df = 3 and I ² is 11%.

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Figure 6

(Analysis 1.5) Child outcomes, observed positive child behaviour

Parent outcomes at end of intervention

Observed positive parenting behaviour

Ten studies analysed the effect of attachment-based interventions on positive parenting behaviour post intervention as measured by independent observation of video-taped interaction between the child and caregivers or coding of audio-taped recordings of parental speech. Measures include Adapted Ainsworth Scales for sensitivity and noninterference, Measurement of Empathy in Adult–Child Interaction, The Dyadic Parent–Child Interaction Coding System, Reflective functioning scale and Emotional Availability Scales. All the reported results indicate a positive effect; two of the individual study effect sizes are very large. The weighted average is large and positive, favouring the treated group and statistically significant. The random effects weighted SMD is 1.56 (95% CI, 0.81–2.31). The forest plot is displayed in Figure 7. There is a very large degree of heterogeneity between the studies; the estimated τ² is 1.19, Q = 119.64, df = 9 and I ² is 92%.

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Figure 7

(Analysis 2.1) Parent outcomes, observed positive parent behaviour

Parenting stress

Nine studies analysed the effect of attachment-based interventions on self-reported post intervention parenting stress as measured by the Parenting Stress Index. Two of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group and statistically significant. The random effects weighted SMD is 0.24 (95% CI, 0.03–0.46.). The forest plot is displayed in Figure 8. There is almost no heterogeneity between the studies; the estimated τ ² is 0.00, Q = 8.22, df = 8 and I ² is 3%.

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Figure 8

(Analysis 2.2) Parent outcomes, parenting stress

Three studies reported the domain scores from the PSI in addition to the total scale score. We did not conduct meta-analysis on each of the domain scores separately, as we deemed the construct validity of the domain scores to be unclear, and thus we chose to only use the total scale score as a comprehensive measure of parenting stress.

Parental depressive symptoms

Three studies analysed the effect of attachment-based interventions on post intervention self-reported depressive symptoms as measured by Beck Depression Inventory. Two of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.59 (95% CI −0.08–1.25.). The forest plot is displayed in Figure 9. There is a small degree of heterogeneity between the studies; the estimated τ ² is 0.13, Q = 3.08, df = 2 and I ² is 35%.

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Figure 9

(Analysis 2.3) Parent outcomes, parental depressive symptoms

Other outcomes

In addition a number of outcomes were reported in a single study only. The outcomes were from a variety of measures: Adult–Adolescent Parenting Inventory, Arnold Parenting Scale, Attachment Q-Sort, Brief parental self-efficacy scale, Child–Parent Relationship Scale, Emotional Availability Self-Report, Erickson scale for supportive presence (based on video tapes), Eyberg Child Behavior Inventory, Indiscriminate Friendliness Interview, Questionnaire Attitudes towards Parenting, Revised child anxiety and depression scale (foster parent report), Revised child anxiety and depression scale (self report), Strengths and Difficulties Questionnaire (self-report), The Behavioral Assessment System for Children and Trauma Symptoms Checklist for Young Children. The effect sizes and 95% CIs are reported in Table 14.

Outcomes at follow-up

Child externalising behaviour problems

Three studies analysed the effect of attachment-based interventions on the externalising behaviour problems of foster and adopted children using sub scales from the Child Behavior Checklist and The Strengths and Difficulties Questionnaire as reported by their caregivers 3–6 months after the intervention was finished. Two of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.04 (95% CI, −0.78–0.87). The forest plot is displayed in Figure 10. There is a large degree of heterogeneity between the studies; the estimated τ ² is 0.45, Q = 13.97, df = 2 and I ² is 86%.

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Figure 10

(Analysis 3.1) Follow up, child externalising behaviour

Child internalising behaviour problems

Two studies analysed the effect of attachment-based interventions on the internalising behaviour problems of foster and adopted children using sub scales from the Child Behavior Checklist and The Strengths and Difficulties Questionnaire as reported by their caregivers 3–6 months after the intervention was finished. One of the reported results indicate a negative effect but the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.32 (95% CI, −0.68–1.32). The forest plot is displayed in Figure 11. There is a large degree of heterogeneity between the studies; the estimated τ ² is 0.43, Q = 5.47, df = 1 and I ² is 82%.

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Figure 11

(Analysis 3.2) Forest plot of comparison: 3 follow up, child internalising behavior

Observed positive parenting

Three studies analysed the effect of attachment-based interventions on positive parenting behaviour as measured by independent observation of video-taped interaction between the child and caregivers or in taped recordings of parental speech samples 3–6 months past the end of the intervention. Measures include Adapted Ainsworth Scales for sensitivity and noninterference, Reflective functioning scale and Emotional Availability Scales. All the reported results indicate a positive effect and the weighted average is positive, favouring the treated group and statistically significant. The random effects weighted SMD favouring the intervention group is 0.54 (95% CI, 0.03–1.06). The forest plot is displayed in Figure 12. There is some degree of heterogeneity between the studies; the estimated τ ² is 0.12, Q = 4.96, df = 2 and I ² is 60%.

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Figure 12

(Analysis 3.3) Follow up, observed positive parenting

Parenting stress

Two studies analysed the effect of attachment-based interventions on self-reported post intervention parenting stress as measured by the Parenting Stress Index. Both the reported results indicate a positive effect and the weighted average is positive, favouring the treated group but not statistically significant. The random effects weighted SMD is 0.60 (95% CI, −0.15–1.35). The forest plot is displayed in Figure 13. There is some degree of heterogeneity between the studies; the estimated τ ² is 0.20, Q = 3.01, df = 1 and I ² is 67%.

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Figure 13

(Analysis 3.4) Follow up, parenting stress

Subgroup analysis and investigation of heterogeneity

The included studies differed in terms of their participants characteristics, duration of the intervention and intervention components. With between two and ten studies in a single meta-analysis, the statistical power to detect heterogeneity of effects was quite low; nevertheless, evidence of statistical heterogeneity was found; in some analyses it was substantial. Due to missing data and invariability between studies on most of the moderators we planned to investigate, it was only possible to investigate the impact of children being adopted versus foster children, child age (<3 years of age vs. 3 years or older), and location (in the family home vs. other locations). We only performed subgroup analysis if there were at least two studies in each subgroup (child overall psychosocial adjustment, child externalising symptoms, observed positive parenting and parenting stress). All the results rely strictly on variation between studies, not within. Making inferences about different effect sizes among subgroups on the basis of between-study differences entails a higher risk compared to inferences made on the basis of within study differences (Oxman & Guyatt, 1992). One should therefore be careful when interpreting estimates that rely on variation between studies. We have drawn no overall conclusion because the analysis is based on a subset of the meta-analyses. The assessment of any difference between the subgroups is based on 95% CIs and interpretation of relationships is cautious.

Child outcomes

Overall psychosocial adjustment

Foster/adopted

Of the ten studies providing effect estimates of the overall child psychosocial adjustment, five used a sample of foster children only and five used a sample of adopted children only. The forest plot for the ten effect estimates is displayed in Figure 14. Pooled results for the two subgroups showed a statistically nonsignificant positive effect of 0.39 (95% CI, −0.11–0.88) for foster children and a statistically significant positive effect of 0.35 (95% CI, 0.10–0.70) for adopted children. There was some degree of heterogeneity of effects among studies in the subgroup of foster children (τ ² = 0.20, I ² = 65%) and for adopted children (τ ² = 0.08, I ² = 54%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by foster/adopted status.

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Figure 14

(Analysis 4.6) Forest plot of comparison: 4 subgroup child outcomes, outcome: 4.6 adopted subgroup child overall psychosocial adjustment

Age

Eight studies used a sample of children on average 3 years or older and two studies used a sample of children on average <3 years. The forest plot for the ten effect estimates is displayed in Figure 15. Pooled results for the two subgroups showed a statistically nonsignificant positive effect of 0.29 (95% CI, −0.01–0.59) for children on average aged 3 years or older and a statistically significant positive effect of 0.78 (95% CI, 0.04–1.52) for children on average <3 years old. There was some degree of heterogeneity of effects among studies in the subgroup of children on average aged 3 years or older (τ ² = 0.10, I ² = 55%) and for children on average <3 years old (τ ² = 0.16, I ² = 44%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by children's age.

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Figure 15

(Analysis 4.7) Forest plot of comparison: 4 subgroup child outcomes, outcome: 4.7 age subgroup child overall psychosocial adjustment

Location

Four studies analysed interventions in the family home and six analysed interventions in another location. The forest plot for the ten effect estimates is displayed in Figure 16. Pooled results for the two subgroups showed a statistically significant positive effect of 0.81 (95% CI, 0.47–1.15) for interventions in the family home and a statistically nonsignificant positive effect of 0.11 (95% CI, −0.09–0.31) for interventions in another location. There was a small degree of heterogeneity of effects among studies in the subgroup of therapy in the family home (τ ² = 0.01, I ² = 10%) and no heterogeneity for therapy in another location (τ ² = 0.00, I ² = 0%). The CIs of the subgroups did not overlap, hence we can not rule out that the effects differ by location.

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Figure 16

(Analysis 4.8) Forest plot of comparison: 4 subgroup child outcomes, outcome: 4.8 location subgroup child overall psychosocial adjustment

Externalising behaviour problems

Foster/adopted

Of the eight studies providing effect estimates of children's externalising behaviour problems, five used a sample of foster children only and three used a sample of adopted children only. The forest plot for the eight effect estimates is displayed in Figure 17. Pooled results for the two subgroups showed a statistically significant positive effect of 0.73 (95% CI, 0.02–1.43) for foster children and a statistically nonsignificant negative effect of −0.03 (95% CI, −0.38–0.24) for adopted children. There was a somewhat large degree of heterogeneity of effects among studies in the subgroup of foster children (τ ² = 0.49, I ² = 79%) and a smaller degree of heterogeneity for adopted children (τ ² = 0.03, I ² = 40%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by foster/adopted status.

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Figure 17

(Analysis 4.9) Forest plot of comparison: 4 subgroup child outcomes, outcome: 4.9 adopted subgroup externalising behaviour

Age

All of the studies used a sample of children on average 3 years or older.

Location

Two studies analysed interventions in the family home and six analysed interventions in another location. The forest plot for the eight effect estimates is displayed in Figure 18. Pooled results for the two subgroups showed a statistically nonsignificant positive effect of 0.68 (95% CI, −1.34–2.71) for interventions in the family home and a statistically nonsignificant positive effect of 0.19 (95% CI, −0.06–0.45) for interventions in another location. There was a very large degree of heterogeneity of effects among studies in the subgroup of therapy in the family home (τ ² = 2.07, I ² = 97%) and a small degree of heterogeneity for therapy in another location (τ ² = 0.02, I ² = 15%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by location.

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Figure 18

(Analysis 4.10) Forest plot of comparison: 4 subgroup child outcomes, outcome: 4.10 location subgroup externalising behaviour

Parent outcomes

Observed positive parenting behaviour

Foster/adopted

Of the ten studies providing effect estimates of observed positive parenting behaviour, five used a sample of foster children only and five used a sample of adopted children only. The forest plot for the ten effect estimates is displayed in Figure 19. Pooled results for the two subgroups showed a statistically significant positive effect of 2.57 (95% CI, 0.84–4.30) for foster children and a statistically significant positive effect of 1.01 (95% CI, 0.56–1.46) for adopted children. There was a very large degree of heterogeneity of effects among studies in the subgroup of foster children (τ ² = 3.31, I ² = 96%) and a large degree of heterogeneity for adopted children (τ ² = 0.15, I ² = 62%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by foster/adopted status.

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Figure 19

(Analysis 5.1) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.1 adopted subgroup observed positive parent behaviour

Age

Seven studies used a sample of children on average 3 years or older and three studies used a sample of children on average <3 years. The forest plot for the ten effect estimates is displayed in Figure 20. Pooled results for the two subgroups showed a statistically significant positive effect of 0.2.19 (95% CI, 0.99–3.38) for children on average aged 3 years or older and a statistically significant positive effect of 0.56 (95% CI, 0.06–1.06) for children on average <3 years old. There was a very large degree of heterogeneity of effects among studies in the subgroup of children on average aged 3 years or older (τ ² = 2.20, I ² = 94%) and a large degree of heterogeneity for children on average <3 years old (τ ² = 0.11, I ² = 60%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by children's age.

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Figure 20

(Analysis 5.4) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.4 age subgroup observed positive parent behaviour

Location

Five studies analysed interventions in the family home and five analysed interventions in another location. The forest plot for the ten effect estimates is displayed in Figure 21. Pooled results for the two subgroups showed a statistically significant positive effect of 0.58 (95% CI, 0.26–0.90) for interventions in the family home and a statistically significant positive effect of 3.29 (95% CI, 1.13–5.45) for interventions in another location. There was some degree of heterogeneity of effects among studies in the subgroup of therapy in the family home (τ ² = 0.06, I ² = 49%) and a very large degree of heterogeneity for therapy in another location (τ ² = 5.38, I ² = 96%). The CIs of the subgroups did not overlap, hence we can not rule out that the effects differ by location.

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Figure 21

(Analysis 5.5) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.5 location subgroup observed positive parent behaviour

Parenting stress

Foster/adopted

Of the nine studies providing effect estimates of parenting stress, seven used a sample of foster children only and two used a sample of adopted children only. The forest plot for the nine effect estimates is displayed in Figure 22. Pooled results for the two subgroups showed a statistically nonsignificant positive effect of 0.20 (95% CI, −0.04–0.43) for foster children and a statistically nonsignificant positive effect of 0.59 (95% CI, −0.01–1.19) for adopted children. There was a low degree of heterogeneity of effects among studies in the subgroup of foster children (τ ² = 0.01, I ² = 96%) and no heterogeneity for adopted children (τ ² = 0.00, I ² = 0%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by foster/adopted status.

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Figure 22

(Analysis 5.6) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.6 adopted subgroup parenting stress

Age

Seven studies used a sample of children on average 3 years or older and two studies used a sample of children on average <3 years. The forest plot for the nine effect estimates is displayed in Figure 23. Pooled results for the two subgroups showed a statistically significant positive effect of 0.34 (95% CI, 0.08–0.60) for children on average aged 3 years or older and a statistically nonsignificant positive effect of 0.04 (95% CI, −0.33–0.40) for children on average <3 years old. There was almost no heterogeneity of effects among studies in the subgroup of children on average aged 3 years or older (τ ² = 0.00, I ² = 1%) and no heterogeneity for children on average <3 years old (τ ² = 0.0, I ² = 0%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by children's age.

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Figure 23

(Analysis 5.7) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.7 age subgroup parenting stress

Location

Four studies analysed interventions in the family home and five analysed interventions in another location. The forest plot for the nine effect estimates is displayed in Figure 24. Pooled results for the two subgroups showed a statistically nonsignificant positive effect of 0.07 (95% CI, −0.21–0.36) for interventions in the family home and a statistically significant positive effect of 0.45 (95% CI, 0.11–0.80) for interventions in another location. There was no heterogeneity of effects among studies in the subgroup of therapy in the family home (τ ² = 0.0, I ² = 0%) and a very small degree of heterogeneity for therapy in another location (τ ² = 0.02, I ² = 12%). The CIs of the subgroups overlapped. There was no evidence to support the hypothesis that the effect differs by location (Figures 25–30).

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Figure 24

(Analysis 5.8) Forest plot of comparison: 5 subgroup parent outcomes, outcome: 5.8 location subgroup parenting stress

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Figure 25

(Analysis 1.1) Funnel plot: child overall psychosocial adjustment

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Figure 26

(Analysis 1.5) Funnel plot of comparison: 1 child outcomes, outcome: 1.5 observed positive child behaviour

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Figure 27

(Analysis 1.2) Funnel plot: child externalising behaviour

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Figure 28

(Analysis 1.3) Funnel plot: 1 child Internalising symptoms

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Figure 29

(Analysis 2.1) Funnel plot: observed positive parent behaviour

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Figure 30

(Analysis 2.2) Funnel plot: parenting stress

Sensitivity analysis

We conduct sensitivity analyses by restricting the included studies to the RCTs and subsequently restricting the remaining RCTs to the most favourable rating for the overall risk of bias judgement. Sensitivity analysis is also conducted across domains of the risk of bias assessment, restricting studies to the most favourable rating for each domain. Sensitivity analysis is only conducted when there are more than two studies left in the analyses.

The analyses are performed separately by outcome, essentially replicating the meta-analyses conducted in the section Effects of interventions.

Child outcomes

Overall psychosocial adjustment

The results of excluding the NRS study, and in addition the study with overall judgement High/Serious risk of bias and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 7 and displayed in a forest plot Figure 31. The child overall psychosocial adjustment outcome lost statistical significance when restricting the analysis to studies assessed Low risk of bias in the missing data domain and the measurement bias domain respectively. Otherwise, there were no appreciable changes in the results following removal of any of the studies.

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Table 7

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	10	0.37	0.10	0.65
NRS	9	0.43	0.13	0.74
NRS and overall judgement high/serious risk of bias	8	0.40	0.08	0.73
Randomisation process: some concerns or high risk of bias	2	0.46	0.15	0.78
Missing data: some concerns/moderate or high/serious risk of bias	5	0.50	−0.08	1.08
Measurement bias: some concerns/moderate or high/serious risk of bias	6	0.22	−0.11	0.55

Note: Restricting studies to RCTs, the most favourable rating on the overall risk of bias judgement and across domains of the risk of bias assessment. SMD with 95% CI. Reporting bias: some concerns/moderate or high/serious risk of bias excluded, only one study remained.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 31

Sensitivity analysis, child overall psychosocial adjustment

Externalising behaviour problems

The results of excluding the NRS studies (there were no RCTs with overall judgement High/Serious risk of bias) and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 8 and displayed in a forest plot, Figure 32. There were no appreciable changes in the results following removal of any of the studies.

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Table 8

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	8	0.37	−0.09	0.83
NRS	6	0.42	−0.23	1.07
NRS and overall judgement high/serious risk of bias	6	0.424	−0.23	1.07
Randomisation process: some concerns or high risk of bias	2	0.03	−0.71	0.76
Missing data: some concerns/moderate or high/serious risk of bias	4	0.43	−0.60	1.47
Measurement bias: some concerns/moderate or high/serious risk of bias	4	0.05	−0.28	0.37
Reporting bias: some concerns/moderate or high/serious risk of bias	2	0.09	−0.47	0.65

Note: Restricting studies to RCTs, the most favourable rating on the overall risk of bias judgement and across domains of the risk of bias assessment. SMD with 95% CI.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 32

Sensitivity analysis, child externalising behaviour

Internalising symptoms

The results of excluding the NRS study (there were no the studies with overall judgement High/Serious risk of bias) and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 9 and displayed in a forest plot, Figure 33. There were no appreciable changes in the results following removal of any of the studies.

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Table 9

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	5	0.20	−0.02	0.42
NRS	4	0.26	−0.04	0.56
NRS and overall judgment high/serious risk of bias	4	0.26	−0.04	0.56
Missing data: some concerns/moderate or high/serious risk of bias	2	0.25	−0.15	0.65
Measurement bias: some concerns/moderate or high/serious risk of bias	3	0.16	−0.10	0.41

Note: Restricting studies to RCTs, the most favourable rating on the overall risk of bias judgement and across domains of the risk of bias assessment. SMD with 95% CI. Randomisation Process: Some concerns or High risk of bias excluded, only one study remained; Deviation Bias: Some concerns/Moderate or High/Serious risk of bias excluded, only one study remained; Reporting Bias: Some concerns/Moderate or High/Serious risk of bias excluded, only one study remained.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 33

Sensitivity analysis, child internalising symptoms

Observed child attachment security

It was not possible to perform sensitivity analysis due to the limited number of studies reporting this outcome.

Observed positive child behaviour

The results of excluding the studies with overall judgment High/Serious risk of bias and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 10 and displayed in a forest plot, Figure 34. The child observed positive behaviour outcome lost statistical significance when restricting the analysis to studies assessed Low risk of bias in the missing data domain. Otherwise, there were no appreciable changes in the results following removal of any of the studies.

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Table 10

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	4	0.39	0.14	0.64
Overall judgment high/serious risk of bias	3	0.41	0.01	0.81
Randomisation process: some concerns or high risk of bias	3	0.34	0.10	0.58
Missing data: some concerns/moderate or high/serious risk of bias	2	0.71	−0.17	1.59
Measurement bias: some concerns/moderate or high/serious risk of bias	3	0.41	0.01	0.81

Note: Restricting studies to the most favourable rating on the overall risk of bias judgment and across domains of the risk of bias assessment. SMD with 95% CI. NRS excluded, all studies were RCT; Deviation Bias: Some concerns/Moderate or High/Serious risk of bias excluded, only one study remained; Reporting Bias: Some concerns/Moderate or High/Serious risk of bias excluded, no studies remained.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 34

Sensitivity analysis, observed positive child behaviour

Parent outcomes

Observed positive parenting behaviour

The results of excluding the studies with overall judgment High/Serious risk of bias and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 11 and displayed in a forest plot (Figure 35). There were no appreciable changes in the results following removal of any of the studies.

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Table 11

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	10	1.56	0.81	2.31
Overall judgment high/serious risk of bias	9	1.33	0.62	2.05
Randomisation process: some concerns or high risk of bias	5	1.65	0.50	2.81
Missing data: some concerns/moderate or high/serious risk of bias	4	1.01	0.19	1.84
Measurement bias: some concerns/moderate or high/serious risk of bias	8	1.22	0.48	1.96

Note: Restricting studies to the most favourable rating on the overall risk of bias judgment and across domains of the risk of bias assessment. SMD with 95% CI. NRS excluded, all studies were RCT; Deviation Bias: Some concerns/Moderate or High/Serious risk of bias excluded, only one study remained.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 35

Sensitivity analysis, observed positive parenting behaviour

Parenting stress

The results of excluding the NRS study, and in addition the study with overall judgment High/Serious risk of bias and studies assessed Some concerns/Moderate or High/Serious risk of bias across the other domains of the risk of bias assessment are provided in Table 12 and displayed in a forest plot (Figure 36).

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Table 12

Sensitivity analysis

	Number of studies	Mean	95% CI
Studies excluded	k	SMD	Lower	Upper
	9	0.24	0.03	0.46
NRS	8	0.27	0.04	0.50
NRS and overall judgment high/serious risk of bias	7	0.29	0.03	0.54
Randomisation process: some concerns or high risk of bias	2	0.13	−0.20	0.47
Missing data: some concerns/moderate or high/serious risk of bias	5	0.27	−0.05	0.58
Measurement bias: some concerns/moderate or high/serious risk of bias	5	0.20	−0.06	0.46
Reporting bias: some concerns/moderate or high/serious risk of bias	2	0.23	−0.36	0.81

Note: Restricting studies to RCTs, the most favourable rating on the overall risk of bias judgment and across domains of the risk of bias assessment. SMD with 95% CI.

Abbreviations: CI, confidence interval; SMD, standardised mean difference.

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Figure 36

Sensitivity analysis, parenting stress

The parent stress outcome lost statistical significance when restricting the analysis to studies assessed Low risk of bias in the randomisation process, missing data domain, the measurement bias domain and reporting bias domain respectively. Otherwise, there were no appreciable changes in the results following removal of any of the studies.

Parental depressive symptoms

It was not possible to perform sensitivity analysis due to the limited number of studies reporting this outcome.

Follow-up

It was not possible to perform sensitivity analyses due to the limited number of studies reporting any of the outcomes at follow up.

Cluster

Finally, we investigated the sensitivity of including the cluster randomised trial (Opiola 2018) using an ICC equal to one. The results of varying the ICC are provided in Table 13. There were no appreciable changes in the results.

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Table 13

Sensitivity analysis

Outcome	Child overall psychosocial adjustment	Observed positive parenting	Parenting stress
ICC	Pooled SMD [95% CI]
1	0.37 [0.10, 0.65]	1.56 [0.81, 2.31]	0.24 [0.03, 0.46]
0.9	0.37 [0.10, 0.65]	1.56 [0.81, 2.31]	0.25 [0.03, 0.46]
0.8	0.37 [0.10, 0.65]	1.56 [0.81, 2.31]	0.25 [0.03, 0.47]
0.7	0.37 [0.10, 0.65]	1.56 [0.81, 2.32]	0.25 [0.03, 0.47]
0.6	0.37 [0.10, 0.65]	1.57 [0.81, 2.32]	0.25 [0.03, 0.47]
0.5	0.38 [0.10, 0.65]	1.57 [0.82, 2.32]	0.26 [0.04, 0.48]
0.0	0.38 [0.11, 0.65]	1.57 [0.82, 2.33]	0.28 [0.05, 0.51]

Note: Varying ICC in the cluster randomised trial.

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Table 14

Other outcomes

Author/year	Measure	Outcome	SMD	Lower CI	Upper CI
Baker (2015)	Emotional Availability Self-Report	Child Capacity to Involve Parent	0.84	−0.24	1.92
Baker (2015)	Emotional Availability Self-Report	Mutual Attunement	1.57	0.35	2.79
Baker (2015)	Emotional Availability Self-Report	Affect Quality	0.06	−0.96	1.08
Baker (2015)	Emotional Availability Self-Report	Hostility	1.35	0.19	2.51
Baker (2015)	Emotional Availability Self-Report	Intrusiveness	0.16	−0.86	1.18
Baker (2015)	Attachment Q-Sort	Security	1.65	0.42	2.88
Barone (2019)	Indiscriminate Friendliness Interview	Childs indiscriminate friendliness	0.14	−0.29	0.57
Bywather (2011)	Eyberg Child Behaviour Inventory	Intensity	−0.27	−0.88	0.34
Bywather (2011)	Strengths and Difficulties Questionnaire	Hyperactive	0.22	−0.39	0.83
Bywather (2011)	Arnold, Parenting Scale		0.35	−0.26	0.96
Mersky (2016)	Eyberg Child Behavior Inventory (ECBI).	ECBI intensity	0.59	0.10	1.08
Mersky (2016)	Eyberg Child Behavior Inventory (ECBI).	ECBI problem	0.63	0.14	1.12
Midgley (2019)	Revised child anxiety and depression scale (self report)	Child anxiety and depression	−0.16	−0.85	0.53
Midgley (2019)	Revised child anxiety and depression scale (foster carer report)	Child anxiety and depression	−0.28	−0.97	0.41
Midgley (2019)	Strengths and Difficulties Questionnaire Self-report	Externalising subscale	−0.05	−0.93	0.83
Midgley (2019)	Strengths and Difficulties Questionnaire Self-report	Internalising subscale	0.11	−0.77	0.99
Midgley (2019)	Strengths and Difficulties Questionnaire Self-report	Total problems	0.03	−0.85	0.91
Midgley (2019)	Brief parental self-efficacy scale	Parental self-efficacy	−0.39	−1.08	0.30
N'zi (2016)	Child–Parent Relationship Scale	Positive Aspects of the Relationship	0.84	−0.28	1.96
Nilsen (2007)	The Behavioral Assessment System for Children	Conduct	0.52	−0.44	1.48
Nilsen (2007)	The Behavioral Assessment System for Children	Aggression	0.15	−0.79	1.09
Nilsen (2007)	The Behavioral Assessment System for Children	Hyperactivity	0.56	−0.40	1.52
Nilsen (2007)	Adult–Adolescent Parenting Inventory.	Inappropriate expectations	0.08	−0.86	1.02
Nilsen (2007)	Adult–Adolescent Parenting Inventory.	Lack of empathy	0.02	−0.92	0.96
Nilsen (2007)	Adult–Adolescent Parenting Inventory.	Parent–child role reversal	−0.20	−1.14	0.74
Nilsen (2007)	Adult–Adolescent Parenting Inventory.	Power differential	0.27	−0.69	1.23
Razuri (2016)	Strengths and Difficulties Questionnaire	Prosocial behavior	0.08	−0.23	0.39
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Anger/Aggression	−0.01	−0.32	0.30
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Posttraumatic Stress—Intrusion	−0.01	−0.32	0.30
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Posttraumatic Stress—Avoidance	−0.08	−0.39	0.23
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Posttraumatic Stress—Arousal	0.13	−0.18	0.44
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Dissociation	0.20	−0.13	0.53
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Sexual concerns	−0.21	−0.54	0.12
Razuri (2016)	Trauma Symptoms Checklist for Young Children	Posttraumatic Stress—Total	0.02	−0.29	0.33
Schoemaker (2020)	Erickson scale for supportive presence (based on video tapes)	Sensitive discipline	0.43	−0.10	0.96
Schoemaker (2020)	Questionnaire Attitudes towards Parenting	Attitudes towards sensitivity	0.36	−0.17	0.89

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Table 15

Other outcomes follow up

Author (year)	Measure	Outcome	SMD	Lower CI	Upper CI
Barone (2019)	Emotional Availability scales, 4th Edition (EAs—Biringen, 2008) by videotaping	Emotional availability: two scales of child's behaviour: responsiveness and involvement.	0.76	0.31	1.21
Barone (2019)	Indiscriminate Friendliness Interview (Chisholm, 1998; Chisholm, Carter, Ames, & Morison, 1995)	Childs indiscriminate friendliness (follow-up)	0.07	−0.38	0.52
Midgley (2019)	Strengths and Difficulties Questionnaire (foster care report)	Total problems	−0.27	−0.96	0.42
Midgley (2019)	Brief parental self-efficacy scale	Parental self-efficacy	0.26	−0.43	0.95
Midgley (2019)	Revised child anxiety and depression scale (self report)	Child anxiety and depression	−0.25	−0.94	0.44
Midgley (2019)	Revised child anxiety and depression scale (foster care report)	Child anxiety and depression	−0.47	−1.16	0.22

Summary of main results

his review focused on the effect of parenting interventions based on attachment theory on child and parent outcomes. The review summarises findings from 44 studies reporting on 27 different samples (19 randomised trials and 8 nonrandomised studies). The meta-analyses are based on 24 studies reporting on 16 samples (14 randomised trials and two nonrandomised studies).

Overall completeness and applicability of evidence

In this review, we included a total of 24 studies in the data synthesis. This number is relatively low compared to the large number of studies (44) meeting the inclusion criteria. The reduction was caused by three different factors. Fifteen studies were judged to have a critically high risk of bias and, in accordance with the protocol, we excluded these from the data synthesis on the basis that they would be more likely to mislead than inform on the size of the effect of the intervention. Five of the 44 studies did not report effect estimates or provide data that would allow the calculation of an effect size.

If all the 44 studies had provided an effect estimate with a lower risk of bias, the final list of useable studies in the data synthesis would have been larger which, in turn, would have provided a more robust literature on which to base conclusions.

We analysed all available child and parent outcomes. However, the small number of studies reporting on child attachment makes us reluctant to draw conclusions, and thus more research is needed.

We found no strong indication of publication bias.

Although we searched for studies including children aged 0–17 most of the studies included in the analyses consisted of relatively young children. The mean age of the children in the included studies was 5.15 years ranging from 0.62 to 10.65 years. The majority of children had been placed in care at a relatively young age. The mean age of placement was 2.31 years ranging from 0.25 to 4.8 years. This is not surprising as attachment based interventions traditionally are offered to families with young children.

Findings from the present review are relevant to all clinicians working with children and parents in foster and adoptive families and suggest that using this type of intervention with this population has clinically relevant positive short-term effects. The findings from the meta-analysis of the outcomes: observed positive parent behaviour, observed positive child behaviour and the overall psychosocial adjustment of the children suggest, that although there is no rigorous evidence, attachment-based interventions may also promote the longer term psychosocial adjustment of children and promote positive family coping. The fact that there were so few studies reporting on the long term effects of attachment-based interventions on all outcomes beyond the 3–6 months follow up is not surprising as longitudinal research is costly and difficult to carry out. However, as stated in the introduction the consequences of placement breakdown to both the children, parents, and society are grim and thus more research should explore this issue further.

Quality of the evidence

Overall the risk of bias in the majority of included nonrandomised studies was high. Six of nine nonrandomised studies were judged overall to be at critical risk of bias and the remaining three were rated serious risk of bias overall. The included studies reporting on RCTs were of lower risk of bias; nine were judged overall to be at critical risk of bias and the majority (23) were rated Some concerns and the remaining three high risk of bias. The risk of bias in randomised studies was examined using Cochranes revised risk of bias tool, RoB 2 (Higgins et al., 2019), and the risk of bias in nonrandomised studies, using the model ROBINS-I, developed by members of the Cochrane Bias Methods Group and the Cochrane Non-Randomised Studies Methods Group (Sterne et al., 2016). We attempted to manage the level of the quality of the evidence in this review by excluding studies judged to be at critical risk of bias using these tools. We believe this process excluded those studies that are more likely to mislead than inform.

Six studies reported the results of an American randomized trial using the ABC intervention: Dozier et al. (2006, 2008, 2009), Bick and Mary (2013), Lewis-Morrarty et al. (2012), and Lind et al. (2017). One publication only reported one outcome, which was not relevant to the present review, and the remaining five studies were rated as in critical risk of bias due to a number of problems primarily caused by a lack of information regarding the number of participants and time points for measurement. We attempted to contact authors, which was successful in one case. However, the author could only provide the means and SDs for a subsample and only from one time point in which the attrition from the trial as reported in the publication exceeded 50%, and thus we deemed the risk of reporting bias to be critical in these five publications.

The fact that only three of the RCT's had a published a priori protocol or a priori analysis plan is concerning, and may suggest that studies within this field are of lower quality than what would be expected, and thus points to the need for increased methodological rigour in future research. However especially for the older studies, it may also just reflect that publishing protocols is or was not standard procedure/expected in this area.

The included studies were relatively small with an average of 72 participants ranging from 14 to 256. In many of the meta-analyses most of the individual study results have CIs crossing 0 making them insignificant. As the individual studies are relatively small and the highest number of studies included in a meta-analysis is 10 the total number of participants is still limited.

We performed sensitivity analyses (where possible) to check whether the obtained results are robust across methodological quality. Although the statistically significant pooled outcomes lost significance in a few instances, the overall conclusions did not change.

There was overall consistency in the direction of effects at end of intervention. Very few the primary study results were negative, that is, most of the effect sizes favoured the treated group. There was a high degree of heterogeneity between studies in some of the analyses, especially in the analyses of child outcomes. In two of five analyses of child outcomes, there were no or a small degree of heterogeneity whereas in two of three analysis of parent outcomes there was no or a small degree of heterogeneity.

Concerning child outcomes, evidence was less consistent for assessments taken at follow up times, 3–6 months post intervention. In addition, for both child outcomes and parent outcomes, there was a high degree of heterogeneity between the studies at follow up and few studies reported data at follow up.

Potential biases in the review process

We performed a comprehensive electronic database search, combined with grey literature searching, and hand searching of key journals. All citations were screened by two independent screeners from the review team, and one review author (NTD) assessed all included studies against inclusion criteria.

We believe that all the publicly available studies on the effect of attachment-based parenting interventions with foster and adoptive families up to the censor date were identified during the review process. However, 21 references were not obtained in full text. Despite attempts to contact the author(s) of all studies with insufficient information, we are still awaiting answers with regard to six studies.

We were unable to comment on the possibility of publication bias as at most ten studies were included in the same meta-analysis. Thus, we cannot rule out that there are still some missing studies.

We believe that there are no other potential biases in the review process as two members of the review team (JH, TEJ, KGE, and ANDA) independently coded the included studies. Any disagreements were resolved by discussion. Further, decisions about the inclusion of studies were made by two members of the review team (TEJ, KGE, and ANDA) and at least one review author (TRF and NTD). Assessment of study quality and numeric data extraction was made by one review author (TRF/NTD/MP) or MKT and was checked by a second review author and two members of the review team (TEJ, KGE, and ANDA).

Agreements and disagreements with other studies or reviews

In a meta-analysis on the effectiveness of preventative attachment interventions on parental sensitivity and infant attachment for at risk populations (k = 70), results suggest that interventions are rather effective at increasing parental sensitivity (d = 0.33) and/or infant attachment (d = 0.20). (Bakermans-Kranenburg et al., 2003). In a systematic review co-registered at Cohrane and Campbell, Barlow et al. (2015) explored the effects of attachment-based parent-infant psychotherapy on parental and infant mental health. This review focused on infants aged 0–24 months within vulnerable families (defined as families in which parents were suffering from mental health issues, drug/alcohol abuse, or were victims of domestic violence). Findings from this review suggest that parent-infant psychotherapy is a promising approach in terms of improving infant attachment security in high-risk families. However, there were no significant differences compared with no treatment or treatment-as-usual for other parent-based or relationship-based outcomes.

In the present review, we found a larger effect size on positive parenting behaviour than what was reported by Bakermans-Kranenburg et al. (2003) and, in contrast to Barlow et al. (2015) we did find other positive effects of attachment-based interventions when compared to treatment as usual. These differences may perhaps be explained by a difference in motivation and socioemotional resources between at-risk biological parents and the population of the present review.

The fact that the reviews by Bakermans-Kranenburg et al. and by Barlow et al. were able report a positive effect on child attachment outcomes is interesting and emphasises the need for more research on the effects of attachment-based interventions on attachment outcomes in foster care and adoption, given that we were only able to extract this outcome from three studies.

Juffer et al. (2017) provides a review and meta-analysis of the effects of Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline (VIPP-SD), which is an intervention based partially on attachment theory with various populations of at-risk parents and vulnerable children (k = 12). In the review, positive effects of VIPP-SD were found on measures of sensitive parenting and socio-emotional child outcomes, which is similar to the findings from the present review.

Schoemaker et al conducted a meta-analytic review (k = 53) examining the effects of all types of parenting interventions in foster care and adoption on eight types of outcomes (Schoemaker et al., 2019). Results show positive effects on four parenting outcomes (sensitive parenting, dysfunctional discipline, parenting knowledge and attitudes, and parenting stress, and on one child outcome (behaviour problems), whereas the review did not find effects for attachment security, child diurnal cortisol levels, or placement disruptions. The findings regarding parental outcomes are broader in scope than what we find in this review, but the finding regarding parental sensitivity is similar to the findings from the present review. These findings may be interpreted as an indication that other types of interventions are as effective as attachment-based interventions on parental behaviour outcomes. Finally, it is also interesting to note that Schoemaker et al. did not find positive effects on child attachment outcomes, and thus it is possible that child attachment security is difficult to change within the relatively short period of time that parenting interventions typically last. It is possible that the positive effects on parenting behaviours, if sustained over time, may lead to possible improvement in child attachment security and a decrease in child disorganised attachment over time, which again highlights the need for more longitudinal research.

Implications for practice

Findings from this review indicate that parenting interventions based on attachment theory increase the overall psychosocial adjustment of children in foster and adoptive families as reported by their caregivers after the intervention. Attachment-based parenting interventions also increase positive parent/child interactional behaviours post intervention based on independent observation and decrease self-reported parenting stress. In summary these findings suggest, that attachment-based parenting interventions have benefits for foster and adopted children and for foster and adoptive parents.

Results from the moderator analyses tentatively suggest that the effects of attachment-based parenting interventions may differ depending on whether the intervention takes place in the family home or in another location (typically a clinical setting). However, based on the present review it is undetermined which location is more beneficial as results were divergent for parent and child outcomes and we were not able to take into consideration other factors that may have an impact on the effect in the analysis.

The evidence regarding the effect of attachment-based parenting interventions on decreasing parental depressive symptoms was inconclusive. Findings from a review of all types of interventions in foster care and adoption (Schoemaker et al., 2019) suggest that other types of interventions are as effective as attachment interventions on parental behaviour outcomes.

In the present review, only three studies explored the effects of attachment-based interventions on measures of child attachment security. This is puzzling given the nature of the interventions. However, it may reflect a lack of reliable and well-established methods for measuring attachment representations in older children, where it is not possible to use behavioral measures such as the Strange Situation Procedure. Recent research suggests that story stem measures may be a reliable clinical tool for measuring attachment representations in older children (Fairchild, 2006), which may be useful for clinicians when assessing if attachment-based interventions increase the attachment security of foster and adopted children.

Very few studies reported on the long-term effects of attachment-based parenting interventions on any outcomes. Findings suggest that attachment interventions increase positive parenting behaviour at follow-up points 3–6 months after the intervention, and this may have implications for practice, as there is a need for clinicians to continuously evaluate the sustainability of treatment results.

Implications for research

The evidence regarding the effects of attachment-based parenting interventions as presented in the present review is highly encouraging from a research perspective. However, the inconclusive evidence regarding the effect of attachment-based interventions at increasing the attachment security in foster and adopted children constitutes a serious flaw in the current evidence base. The fact that so few studies measured child attachment as an outcome was surprising given the nature of the interventions, and thus due to the low power, the results of the meta-analysis on child attachment security should not be seen as evidence that there is no effect of attachment-based interventions on child attachment security. Rather the results are inconclusive at this point, suggesting a need for more research meassuring attachment as an outcome. Similarly, only one usable study collected data on attachment disorganisation and thus we were unable to conduct a meta-analysis using attachment disorganisation as an outcome, even though this would have been an extremely valuable contribution to the current knowledge base. Theoretically, it is possible that child attachment security and/or attachment disorganisation may be difficult to impact within the relatively short period of time that parenting interventions typically last. It is possible that if post-intervention improvements in parenting behaviours are sustained over time, it may lead to possible improvement in child attachment security and a decrease in child disorganised attachment, and thus it would be particularly important for future research to explore attachment outcomes over a longer period of time.

Ten studies analysed the effect of attachment-based interventions on positive parenting behaviour post intervention. There was a very large degree of heterogeneity between the studies and inconsistency in the magnitude of the effect sizes with two very large effect sizes. These two very large effect sizes might in part be considered as a result of the use of observations of parenting behaviour as part of a clinical assessment. It may be argued that these measures have a limited ecological validity as the behaviour displayed by highly motivated parents who know that they are being carefully observed, and who have just completed an intervention consisting in part of direct guidance on parent/child interactional behaviours, may not be representative of what their parenting is like in everyday life or in less ideal circumstances when they are tired or frustrated or when their child is resistant or displaying behaviour problems. Rather, the observational measures may be said to measure the ideal parenting which the parent is capable of under optimal circumstances, and given that foster and adoptive parents as a group consisting of resourceful individuals who voluntarily participated in interventions, it is in our view not surprising that when receiving the intervention they may be able to improve their parenting skills dramatically - at least within a clinical assessment in which they know that they are being observed.

Furthermore, very few studies reported on the long-term effects of attachment-based parenting interventions on any outcomes, but findings suggest that attachment interventions increase positive parenting behaviour at follow-up points 3–6 months after the intervention. Within the present review it was not possible to conduct a meta-analysis using placement stability or breakdown as an outcome. This emphasises the need for future longitudinal research in the prevention of placement breakdown.

Finally, results of the single factor subgroup analyses suggest that the effects of interventions may differ depending on whether interventions take place in the family home or in another location. However, within the present review, we were unable to determine which location is more beneficial as firstly results were opposite for parent and child outcomes, and secondly we cannot be sure that any of the differences were not caused by other factors than location. Therefore it would be valuable for future trials to test the effects of location using the same intervention and target population.

Characteristics of included studies

Characteristics of excluded studies

Child outcomes

Parent outcomes

Follow Up

Subgroup Child outcomes

Subgroup Parent outcomes