Mindfulness as a pathway to reducing anger rumination and aggression in male prisoners

Abstract

Mindfulness has been associated with reductions in anger rumination and aggressive behaviour, making it particularly relevant in prison settings.

Aim

This study examined the relationship between trait mindfulness, anger rumination and aggression in a sample of 187 male prisoners, aged between 22 and 77 years (M = 41.20, SD = 11.95), with a prison sentence in months of M = 86.42, SD = 97.8.

Method

Self-report measures were used to assess trait mindfulness, anger rumination and aggression (physical aggression, verbal aggression, anger and hostility).

Results

Negative correlations were found between trait mindfulness and the different dimensions of aggression, as well as between trait mindfulness and anger rumination. Additionally, anger rumination was positively correlated with all forms of aggression. The regression analyses revealed that trait mindfulness significantly predicted lower levels of all types of aggression, with the greatest impact being on anger. The mediation analyses pointed to anger rumination significantly mediating the relationship between trait mindfulness and anger, hostility and overall aggression.

Conclusions

Our findings highlight the relevance of addressing cognitive mechanisms such as anger rumination to understanding aggressive behaviour in prison environments. While causal conclusions cannot be drawn, the results have implications for the use of interventions aimed at increasing mindfulness in prison populations.

Keywords

Aggression anger rumination mindfulness prisoners

Introduction

Research has evidenced a strong association between rumination and aggressive behaviours in a number of population settings. In penitentiary settings, where factors such as deprivation of liberty, stress, isolation and lack of control over circumstances predominate, rumination can play a crucial role in exacerbating aggression. However, studies on the relationship between rumination and aggression, or any other cognitive process that might mediate such an association, are limited in prison settings.

This is particularly important if we consider the harmful consequences aggression may have for both the prisoners themselves (and their rehabilitation process) and for other inmates and professionals working at the institution. Mindfulness-based interventions (MBIs) have been successfully applied in structured therapies such as mindfulness-based cognitive therapy, mindfulness-based stress reduction (MBSR), and relapse prevention programmes for addictions, as well as integrated into broader therapeutic approaches like dialectical behavior therapy and acceptance and commitment therapy (Hervás et al., 2016). In this sense, numerous studies support their efficacy across a variety of populations and settings. In community samples, MBSR programmes have shown sustained improvements in symptoms of depression and anxiety up to two years after the intervention (Madson et al., 2018). Among university students, MBIs have proven effective in reducing depression, anxiety, and stress (Zuo et al., 2023), with promising results also observed in online formats (Karing, 2022).

Previous studies have explored the mechanisms by which mindfulness may reduce aggressive behaviour. Peters et al. (2015) found that anger rumination significantly mediated the relationship between specific facets of mindfulness (observing, describing, acting with awareness, nonjudging of inner experiences, nonreactivity to inner experiences) and aggression in a non-clinical student population. Their findings emphasised the role of nonjudging and present-centred awareness in lowering aggression through reduced anger rumination. However, their study was conducted with a general university sample and did not examine the applicability of these mechanisms in high-risk or forensic populations.

At the clinical level, a meta-analysis of 142 studies (N = 12,005) found that MBIs were significantly more effective than no-treatment and various active control conditions, with effects comparable to well-established psychological treatments, particularly in cases of depression, chronic pain, and substance-use disorders (Goldberg et al., 2018). In incarcerated populations, MBIs have also been associated with reductions in stress, depression, anxiety, and criminogenic needs such as impulsivity, anger, and substance use (Per et al., 2019), with preliminary evidence suggesting that these benefits may extend beyond release from prison (Carmo et al., 2022). Specifically, Han’s (2022) meta-analysis showed a significant impact on anxiety and mindfulness, and a moderate effect on depression and emotional distress. These practices have also contributed to improved emotional management and coping with difficulties (Maroney et al., 2021). In controlled studies, mindfulness has also shown a significant reduction in anxiety and depression compared to physical activity programmes in inmates with mental disorders (Gallego et al., 2023).

Furthermore, a systematic review of mindfulness-based programmes in prisons (Derlic, 2020) revealed benefits such as greater self-compassion, self-understanding, lower recidivism, reductions in violence and aggression, and greater self-awareness, even after brief interventions. In addition, individual intervention studies have also reported positive effects of mindfulness-based programmes in incarcerated samples (Zhang et al., 2022). These findings support the growing interest in examining the role of mindfulness in prison contexts.

Aggression and anger rumination

Aggressiveness refers to the predisposition to engage in both verbal and physical aggressive behaviours, to hold hostile cognitions and to experience and express anger (Buss and Perry, 1992). In this sense, aggressive behaviours are a common problem in prison environments (Fazel et al., 2016), being associated with higher rates of violent reoffending (Mooney and Daffern, 2015). Rumination is one such factor that plays a critical role in individual aggressiveness, and it is important to study the relationship between these two constructs.

This psychological construct refers to a maladaptive pattern in the regulation of thought and emotion and is characterised by an automatic and repetitive focus on negative internal or external experiences (Martin and Tesser, 1996; Nolen-Hoeksema and Morrow, 1991). This involves an individual returning repeatedly to disturbing thoughts, worries and events from the past or future, potentially intensifying feelings of frustration and hostility. Indeed, studies have reported that people with a tendency to ruminate are more likely to experience intense emotions of anger and to exhibit aggressive behaviour in response to provocation (Lyubomirsky and Nolen-Hoeksema, 1995), that is, they would have a greater tendency towards revenge after interpersonal conflict (Barber et al., 2005).

Specifically, anger rumination refers to an unintentional and recurrent cognitive process that emerges and is maintained after a personally significant anger experience (Sukhodolsky et al., 2001), with this being a negative emotion resulting from social conditions that may involve threat or frustration (Besharat and Shahidi, 2010). Hence, anger rumination entails repetitive thinking about angry moods, the consequences and causes of anger episodes, and thoughts of revenge (Denson et al., 2013; Quan et al., 2019) affecting the duration, intensity and form of expression of anger (Contreras and Novaco, 2023). Thus, rumination may intensify the feeling of hostility by amplifying anger, imagining violent reprisals (Contreras et al., 2021), and increasing the likelihood of a negative behaviour (Bushman et al., 2005). This is known as ‘feeding the flame’, a cycle which enhances negative affect, undermining an individual's social adjustment (Bushman, 2002).

In this regard, anger rumination has been shown to be a robust predictor of high levels of aggression in both correlational (e.g. García-Sancho et al., 2016; White and Turner, 2014) and experimental studies (e.g. Bushman, 2002). Additionally, taking into account both proactive and reactive aggressive behaviours (Wang et al., 2018), anger rumination even predicts aggressive tendencies through its relationships with variables such as emotional dysregulation and emotional intelligence (Martino et al., 2015), poor psychosocial functioning, low adherence to treatment and poor therapeutic response. It is thus a highly relevant transdiagnostic dimension (González Pandoa et al., 2018), that helps to understand and explain antisocial and criminal behaviours (du Pont et al., 2017), while also clarifying the shared elements of these variables and the specific characteristics of each. This transdiagnostic approach allows the design of individualised intervention strategies tailored to each patient, as well as group interventions targeting disorders or behaviours that share common underlying processes. Such a perspective may be especially useful in settings with high demand for care and limited therapeutic resources (González Pandoa et al., 2018), such as the prison context.

Mindfulness, anger rumination and aggression

Mindfulness refers to the moment-by-moment awareness of thoughts, feelings, bodily sensations and the environment around us (Zhang et al., 2021). That is, mindfulness implies focusing on the present moment (‘the here and now’), accepting it without judgement, and consciously shifting attention away from past or future events. The benefits of practising mindfulness include enhanced response flexibility, decreased reactivity and improvements in interpersonal relationships (Davis and Hayes, 2011).

Although mindfulness is most commonly understood as a state, it can also be considered a stable trait involving capacities such as self-regulation of attention maintained in the present moment, accompanied by attitudes such as kindness and acceptance. Mindfulness practice supports the development of these capacities and attitudes, making it a trainable skill through both formal practices, such as meditation, and informal ones, such as mindful walking with the aim of increasing mindfulness as a trait (Hervás et al., 2016).

Mindfulness can help reduce rumination on negative thoughts and unpleasant emotions (Teasdale et al., 2003). In fact, studies have reported a negative relationship between trait mindfulness and rumination (e.g. Brown and Ryan, 2003) and between mindfulness as a meditation practice and rumination (e.g. Holzel et al., 2011; Ramel et al., 2004). Research on its effects on anger rumination, however, remains limited. Nonetheless, studies such as that by Borders et al. (2010) have shown that anger rumination partially mediates the effect of trait mindfulness on anger and aggression. Similarly, Takebe et al. (2015) demonstrate that mindfulness reduces anger rumination, pointing to its effectiveness in clinical practice with individuals with anger problems. In this sense, an accepting approach to the present will allow a person to experience events that trigger anger without the need to judge them, thus diminishing the impulse to ruminate (e.g. Eisenlohr-Moul et al., 2016).

Furthermore, mindfulness promotes greater self-awareness of internal states and personal values, which would lead to less aggression (Borders et al., 2010). Indeed, it has already been successfully tested in interventions designed to decrease aggressive behaviour (e.g. Christopher et al., 2018; Gillions et al., 2019; Ribeiro et al., 2019; Tao et al., 2021) and self-reported anger (e.g. Deffenbacher, 2016). In the same vein, previous studies have evidenced a consistent negative relationship between mindfulness and aggression as measured in terms of physical aggression, verbal aggression, anger and hostility (e.g. Heppner et al., 2008; Singh et al., 2007a). The explanation appears to lie in mindfulness allowing for effective adaptive regulation of emotions that are difficult to manage (Bishop et al., 2006), leading a person to be less reactive and defensive to provocations, allowing individuals to view potentially upsetting experiences, thoughts and emotions as temporary events within broader contexts, thus reducing anger (Feldman et al., 2010) increasing feelings of connection with, and empathy towards, others (e.g. Shonin et al., 2015).

Study aims and hypotheses

Aggression should be both prevented and addressed through targeted interventions. Consequently, it is crucial to identify the cognitive mechanisms that contribute to it, making this area of study highly valuable from both a theoretical and practical perspective.

Accordingly, the general aim of this study was to examine the role of trait mindfulness in its association with aggression, as measured through physical and verbal aggression, hostility and anger, and its potential effect through anger rumination in the prison population. The specific aims were to study the relationship between trait mindfulness and aggression and trait mindfulness and anger rumination, to determine the impact of anger rumination on aggression, and to explore how anger rumination acts as a mediator in the relationship between trait mindfulness and aggression.

In light of the above aims, we proposed the following research hypotheses: (1) higher trait mindfulness scores will be associated with lower aggression scores (physical aggression, verbal aggression, anger and hostility); (2) higher trait mindfulness scores will be associated with lower anger rumination scores; (3) anger rumination will be positively associated with the different types of aggression (physical aggression, verbal aggression, anger and hostility); (4) anger rumination will significantly mediate the relationship between trait mindfulness and aggression (physical aggression, verbal aggression, anger and hostility), such that higher levels of trait mindfulness will be associated with lower aggression scores via lower levels of anger rumination.

Methodology

Procedure

First, we contacted the Ocaña I prison (Spain) which housed approximately 350 inmates at the time of data collection. Once the penitentiary facility had agreed to collaborate and had been informed of the inclusion and exclusion criteria, the potential participants were randomly selected by means of a double-blind procedure that safeguarded their anonymity. Subsequently, the participants were informed about the study and voluntarily signed the informed consent form, which was adapted to the legislative nature of prison regulations. Data were collected over a six-month period in small group sessions. Each session lasted approximately 60 min. All questionnaires were completed on paper, and participants typically took around 30–40 min to finish them (depending on the participants' pace). The questionnaires were completed with the help of a prison officer who had been previously trained to ensure that the data were collected in a homogenous way. Only fully completed questionnaires were included in the final dataset, and cases with missing data were excluded from the analysis. The study was approved by the corresponding research ethics committee (22/10/2020, Ref. N.° 567).

Participants

A cross-sectional study was designed and applied to a sample of prison inmates, comprising 187 male participants with ages ranging between 22 and 77 years (M = 41.20, SD = 11.95). In terms of educational level, 49.5% of the participants had completed secondary education, 27.1% primary education, 13% university education, 4.7% vocational training, while 4.2% had not completed primary education and 1.5% had postgraduate qualifications. The duration of the participants’ sentences ranged between three and 696 months (M = 86.42, SD = 97.8).

The following inclusion criteria were established: (1) being sufficiently literate (reading and writing); (2) having sufficient Spanish language skills; (3) giving signed informed consent. The exclusion criteria were as follows: (1) presenting physical or psychological problems that would impede participation; (2) having committed offences while under the effects of drugs or alcohol; (3) presence of neurological damage.

Participants whose offences were committed under the influence of alcohol or drugs were excluded to reduce potential confounding. Substance-related aggression may be driven by distinct mechanisms, such as pharmacological disinhibition, altered risk perception due to psychotic symptoms, or substance-specific effects on aggression (e.g. Allen and Anderson, 2018; De Sousa Fernandes Perna et al., 2016).

Materials

Sociodemographic questionnaire. An ad hoc questionnaire was designed to collect the relevant data on a selection of sociodemographic variables, including age, level of education and length of sentence.

The Anger Rumination Scale (ARS; Sukhodolsky et al., 2001 , Spanish adaptation by Ramos-Cejudo et al., 2020 ). This 19-item self-report questionnaire measures a person's tendency to focus attention on angry thoughts and memories of present and past anger episodes. It consists of four subscales corresponding to the four basic components of anger rumination: angry afterthoughts (‘I re-enact the anger episode in my mind after it has happened’), thoughts of revenge (‘When someone makes me angry, I can’t stop thinking about how to get back at this person’), angry memories (‘I keep thinking about events that angered me for a long time’) and understanding of causes (‘I analyse events that make me angry’). Each item is scored on a Likert-type scale (from 1 = almost never, to 4 = almost always). The scores can be summed to obtain both a global score and separate scores for each subscale, thus facilitating an overall or specific analysis, according to the aims of the particular study. The present work only uses the global score. The original version of this instrument showed good validity and reliability (α = .93) (Sukhodolsky et al., 2001), while the Cronbach's alphas for each subscale in the Spanish version (Ramos-Cejudo et al., 2020) ranged between .69 and .83. The reliability of the overall scale in the present study was α = .93.

The Short Form Buss-Perry Aggression Questionnaire ( Diamond and Magaletta, 2006 ). This is a 12-item short form of the Buss-Perry Aggression Questionnaire (BPAQ; Buss and Perry, 1992), which originally comprised 29 items. The questionnaire assesses four dimensions of aggression: physical aggression (‘Given enough provocation, I may hit another person’), verbal aggression (‘I can’t help getting into arguments when people disagree with me’), anger (‘I sometimes feel like a powder keg ready to explode’) and hostility (‘At times I feel I have gotten a raw deal out of life’). The items are scored on a five-point Likert-type scale from 1 (very unlike me) to 5 (very like me), evaluating self-perceived aggressive behaviours and attitudes. It yields specific scores for each of the subscales and a total score that reflects the respondent's general level of aggression. In the study by Diamond and Magaletta (2006), the Cronbach's alphas for each of the subscales ranged from .66 to .77. Internal consistency in the present study was found to be α = .87 for the complete scale and α = .74, α = .63, α = .82 and α = .74 for the subscales of physical aggression, verbal aggression, anger and hostility, respectively.

Freiburg Mindfulness Inventory-14 ( Pérez-Verdusco and Laca-Arocena, 2017 ). This is a brief version of the original Freiburg Mindfulness Inventory designed by Walach et al. (2006). Although there is no universally agreed-upon definition of mindfulness, the FMI-14 focuses on core facets such as attention and acceptance, which are particularly relevant to the emotional self-regulation processes examined in this study: attention, self-control, acceptance and self-perception, emphasising aspects such as acceptance or alertness, and is most suitable for use with persons that may be unfamiliar with meditation. It comprises 14 items, rated on a Likert-type scale from 1 (‘rarely’) to 4 (‘almost always’) (e.g. ‘I am open to the experience of the present moment’, ‘I accept unpleasant experiences’). This instrument was selected for its brevity, strong psychometric properties (in the work by Pérez-Verdusco and Laca-Arocena (2017), reliability was α = .80, while in the present study, we obtained α = .84.), and suitability for populations with no prior experiences in meditation such as incarcerated individuals. In the present work, we used the overall score, obtained by summing the responses to each item.

Data analysis

A quantitative approach was adopted in examining the relationships between trait mindfulness, anger rumination, and aggression (physical aggression, verbal aggression, anger, and hostility), with a particular emphasis on mediation analysis to explore the underlying mechanisms of these variables. Firstly, we estimated the descriptive statistics for all the variables under study (means and standard deviations) in order to have an overview of the data. Secondly, and after confirming the normal distribution of the data, Pearson correlations were computed to identify the initial bivariate relationships, allowing us to verify the existence of significant associations between the study variables and to justify the subsequent analyses.

Thirdly, we conducted linear regression analyses to assess the impact of trait mindfulness on the various dimensions of aggression. A stepwise multiple regression model was then implemented to determine whether anger rumination modulated the relationship between trait mindfulness and aggression.

Finally, PROCESS SPSS (Hayes, 2012; Hayes and Rockwood, 2017), Version 4.2, was used to perform a mediation analysis, for the purpose of evaluating the mediating role of anger rumination. Model 4 Simple Mediation was applied, with trait mindfulness as the independent variable (X), anger rumination as the mediating variable (M) and the dimensions of aggression as dependent (Y). We used 10,000 bootstrap samples to estimate the 95% confidence intervals of the indirect effects.

Results

Descriptive statistics

Table 1 shows the descriptive statistics of the variables under study. The results reveal relatively low levels of aggression; specifically, the participants presented a greater tendency to physical aggression compared to verbal aggression, while also appearing to experience hostility more regularly than anger and the two types of aggression. With regard to anger rumination, the results suggest the participants have a low tendency to experience such thoughts. Regarding trait mindfulness, the participants presented moderately high levels, albeit with considerable variation in the levels.

Table 1.

Descriptive statistics of the main study variables.

	M (SD)	Min	Max
Total BPAQ-SF	2.2 (0.8)	1	5
Physical aggression	2.3 (1.1)	1	5
Verbal aggression	2.1 (0.8)	1	5
Anger	2.1 (1.1)	1	5
Hostility	2.4 (1.1)	1	5
Total ARS	2.2 (0.7)	1	5
Total FMI-14	40.3 (8.7)	14	56

Note. M: mean; SD: standard deviation; Md: median; Min: minimum; Max: maximum; BPAQ-SF: Short Form Buss-Perry Aggression Questionnaire; ARS: Anger Rumination Scale; FMI-14: Freiburg Mindfulness Inventory-14.

Correlation analysis

Table 2 shows the bivariate correlations between the study variables. Total aggression was positively and significantly correlated with all its subscales (physical aggression, verbal aggression, anger and hostility). Anger rumination was correlated with all the subscales of aggression, as well as with the total aggression score, revealing that higher levels of anger rumination are associated with higher levels of aggression in all its forms. Trait mindfulness was negatively and significantly correlated with anger rumination and with all the dimensions of aggression (including total aggression). In the case of verbal aggression, the negative correlation with trait mindfulness was also significant but weaker compared to the other aggression subscales.

Table 2.

Analysis of the correlations found in the study.

	1	2	3	4	5	6	7
1. Total BPAQ-SF	-	.758**	.735**	.909**	.737**	.747**	−.338**
2. Physical aggression	.758**	-	.418**	.669**	.258**	.446**	−.215**
3. Verbal aggression	.735**	.418**	-	.563**	.445**	.522**	−.178*
4. Anger	.909**	.669**	.563**	-	.600**	.662**	−.301**
5. Hostility	.737**	.258**	.445**	.600**	-	.689**	−.279**
6. Total ARS	.747**	.446**	.522**	.662**	.689**	-	−.200*
7. Total FMI-14	−.338**	−.215**	−.178*	−.301**	−.279**	−.200*	-

Note. BPAQ-SF: Short Form Buss-Perry Aggression Questionnaire; ARS: Anger Rumination Scale; FMI-14: Freiburg Mindfulness Inventory-14.

*p < .05, **p < .001.

Regression analysis

Linear regression analyses were conducted to assess the impact of trait mindfulness on total aggression and the different forms of aggression (physical aggression, verbal aggression, anger and hostility). As shown in Table 3, trait mindfulness significantly predicts lower physical aggression, verbal aggression, anger, hostility, and total aggression. Although the effect size varied across the different forms of aggression, the greatest influence of trait mindfulness was observed as a predictor of anger (R² = .091), while the lowest influence was found in verbal aggression (R² = .032). Thus, higher levels of trait mindfulness are associated with lower expressions of aggressive and hostile behaviour.

Table 3.

Results of linear regression analyses for the prediction of aggression, anger and hostility based on trait mindfulness.

Dependent variable	Predictor variable	B	SE	Beta	t	p	R ²
Physical aggression	Total FMI-14	−0.028	0.010	−0.215	−2.764	.006	.046
Verbal aggression	Total FMI-14	−0.017	0.007	−0.178	−2.289	.023	.032
Anger	Total FMI-14	−0.040	0.010	−0.301	−3.991	<.001	.091
Hostility	Total FMI-14	−0.035	0.010	−0.279	−3.634	<.001	.078
Total aggression	Total FMI-14	−0.018	0.007	−0.200	−2.434	.016	.040

Note. B: non-standardised coefficient; SE: standard error associated with coefficient B; Beta: standardised coefficient; t: indicates whether coefficient B is significantly different from zero; p: shows whether the result is significant (< .05); R²: proportion of variance explained by the model; FMI-14: Freiburg Mindfulness Inventory-14.

Following the above, a multiple linear regression analysis was conducted, which included the variable of anger rumination and mindfulness as the predictor variable. As reflected in Table 4, anger rumination was a significant predictor in all the models, showing a positive effect on physical aggression, verbal aggression, anger, hostility and total aggression. In some cases - namely, physical aggression, verbal aggression and total aggression - trait mindfulness loses its significance when anger rumination is incorporated, suggesting complete mediation. Meanwhile, for hostility and anger, the mediation is partial, given that trait mindfulness remains significant, albeit with a smaller effect. It is worth noting that R² increases in all the models when anger rumination is included, indicating that this moderating variable accounts for most of the variance in the dependent variables.

Table 4.

Results of the regression models.

Dependent variable	Predictor variable	B	SE	Beta	t	p	R ²
Physical aggression	Total FMI-14	−0.099	0.078	−0.108	−1.274	.205	.19
	Total ARS	0.679	0.118	0.440	5.772	< .001
Verbal aggression	Total FMI-14	−0.060	0.074	−0.068	−0.805	.422	.25
	Total ARS	0.563	0.082	0.502	6.888	< .001
Anger	Total FMI-14	−0.132	0.009	−0.132	−2.087	.039	46
	Total ARS	0.991	0.098	0.638	10.094	< .001
Hostility	Total FMI-14	−0.018	0.008	−0.137	−2.177	.031	.48
	Total ARS	0.653	0.093	0.682	10.375	< .001
Total aggression	Total FMI-14	−0.108	0.078	−0.108	−1.274	.205	.19
	Total ARS	0.446	0.118	0.440	5.772	< .001

Mediation analysis

Mediation analyses were performed to examine the role of anger rumination as a mediating variable in the relationship between trait mindfulness and the other independent variables (total aggression, physical aggression, anger and hostility). The Sobel test was used to measure the significance of the indirect effects. Table 5 details the results for each variable.

Table 5.

Results of mediation analyses with rumination on anger as a mediator.

Dependent variable	Predictor	Direct effect	SE	t	p	Indirect effect (B)	SE (indirect)	Sobel (z)	p (Sobel)	Mediation type
Physical aggression	Total FMI-14	−0.099	0.078	−1.274	.205	0.679	0.118	−1.54	> .05	Complete
Verbal aggression	Total FMI-14	−0.060	0.074	−0.805	.422	0.563	0.082	−1.82	> .05	Complete
Anger	Total FMI-14	−0.132	0.009	−2.087	.039	0.991	0.098	−2.34	< .05	Partial
Hostility	Total FMI-14	−0.018	0.008	−2.177	.031	0.653	0.093	−2.51	< .05	Partial
Total Aggression	Total FMI-14	−0.108	0.078	−1.274	.205	0.446	0.118	−2.75	< .05	Complete

Note. B: non-standardised coefficient; SE: standard error associated with coefficient B; t: t-statistic of direct effect; p: value associated with direct effect; FMI-14: Freiburg Mindfulness Inventory-14.

As can be seen, anger rumination significantly mediates the relationship between trait mindfulness and various forms of aggression. For the variables of anger, hostility and total aggression, significant indirect effects were found, corroborating the mediating role of anger rumination. In the cases of physical and verbal aggression, although complete mediation was found, the indirect effects failed to reach statistical significance in the Sobel test. Figure 1 shows the direct and indirect effects of trait mindfulness on the aggression variables.

Figure 1.

Mediation model showing the effects of trait mindfulness on anger, hostility and total aggression mediated by anger rumination.

Additional analyses

To address concerns regarding potential conceptual overlap between the ARS and the anger and hostility subscales of the BPAQ-SF, additional regression and mediation analyses were conducted using an adjusted total aggression variable composed only of the physical and verbal aggression subscales. Results from these supplementary analyses replicated the original pattern of findings: anger rumination remained a significant predictor and mediator of the relationship between trait mindfulness and aggression, while the direct effect of mindfulness was non-significant. These findings confirm the robustness of the proposed mediation model. The full results of these analyses are presented in Supplemental Tables S1 and S2.

Discussion

The results of the present study provide evidence of the significant role of trait mindfulness and anger rumination as predictors of different forms of aggression in prison populations. Specifically, the findings underscore the negative association between trait mindfulness and aggression, which appears to be partly explained by its relationship with anger rumination.

Relationship between trait mindfulness, anger rumination and aggression

Our results reveal a significant negative relationship between trait mindfulness and aggression, adding strength to the results of previous studies indicating that higher mindfulness may contribute to lower aggression, acting as a protective factor (e.g. Brown and Ryan, 2003; Heppner et al., 2008). Nonetheless, the size of the effect varies according to the type of aggressive behaviour, appearing to have a greater impact on the regulation of intense emotions, such as anger, while having a more limited effect on verbal aggression. This may be due, at least in part, to the relatively low baseline scores in verbal aggression observed in the sample, which could have reduced the variance and limited the potential for detecting stronger associations. The greater influence on anger is consistent with the theory that mindfulness facilitates emotion regulation by allowing for greater awareness and acceptance of emotions without impulsive reactivity (Shapiro et al., 2006). Thus, the effects of trait mindfulness are significant and underline its potential role in interventions designed to reduce aggressive behaviour.

These findings are particularly important, given that previous studies have shown that prison inmates typically present high levels of aggression as an emotional response frequently related to an incapacity to regulate intense negative emotions such as anger (Fleisher and Decker, 2001). These findings align with prior research, such as the study by Shonin et al. (2013), which found that mindfulness interventions may effectively reduce aggression among inmates. In correctional settings, where anger episodes can trigger conflicts and aggressive behaviours, inmates’ ability to regulate such emotions through mindfulness might be a key factor in decreasing violence in prisons, as well as reoffending, facilitating the social reintegration of former detainees.

Additionally, anger rumination was significantly and positively correlated with all forms of aggression, which is also consistent with the results of previous research reporting that the tendency to ruminate on anger intensifies the negative feelings that lead to different aggressive behaviours. This pattern suggests that anger rumination is a key factor in perpetuating aggressive behaviour and that reducing it could play a crucial role in diminishing aggressive behaviour. This is especially important in prison settings, where inmates are often immersed in a high-stress environment, where hostile interactions and conflicts may amplify rumination and, in turn, aggressive behaviour. Additionally, extended periods of isolation or limited social contact (common in many prison environments) may also exacerbate anger rumination, as suggested by previous research (e.g. Andersen et al., 2001; Haney, 2018).

Anger rumination as mediator

The higher R² values observed for anger and hostility suggest that these internal, affective dimensions of aggression are more strongly predicted by trait mindfulness and anger rumination. These findings indicate that mindfulness and rumination influence primarily the internal regulation of intense emotional states (such as anger and hostile thoughts) rather than the external expression of aggression. In contrast, more externalised behaviours, such as physical and verbal aggression, may be shaped by other unmeasured variables, such as situational triggers or impulsivity, which were not accounted for in the current model.

The increase in explained variance observed in all the models implemented, particularly in hostility and anger underlines the critical role of anger rumination as a mediating factor, coinciding with previous findings (e.g. Peters et al., 2015). This supports the notion that mindfulness may reduce aggression, partly because it helps individuals lower their levels of anger rumination, which, in turn, decreases the tendency to aggressive behaviour. In the cases of physical aggression, verbal aggression and total aggression however, the inclusion of anger rumination led to the loss of significance of trait mindfulness, indicating a full mediation. This suggests that mindfulness does not directly reduce these behaviours but does so indirectly by mitigating ruminative tendencies. In other words, individuals with higher mindfulness may show lower aggression not because mindfulness inherently inhibits aggressive acts, but because it reduces the repetitive, anger-focused thoughts that fuel such behaviours, this finding reinforces the conceptual role of rumination as a key pathway linking mindfulness to aggression, especially in forms of aggression less dependent on emotional introspection. These findings are consistent with those of previous studies, such as that by Borders et al. (2010), who reported that rumination significantly increases levels of anger and aggression, while trait mindfulness, by promoting mindfulness and non-reactive attention, can diminish rumination and thus reduce aggression.

It is worth highlighting that, despite anger rumination fully mediating in the cases of physical and verbal aggression, the indirect effects were not significant, which might suggest that rumination does not play such a decisive role in these forms of aggression. This coincides with previous studies in which the relationship between rumination and physical aggression is less clear or not always significant (Bushman et al., 2005), arguably due to this type of aggression tending to be influenced by other factors, such as impulsivity or a lack of direct emotion regulation (e.g. Giancola, 2000). In this sense, mindfulness has been associated with lower levels of impulsivity (e.g. Leshem et al., 2024), which may help explain its potential influence on physical aggression. Although impulsivity was not directly assessed in the present study, future research could benefit from examining this pathway more explicitly. Additionally, in prison environments, where physical conflicts may be linked to defending social status or survival within established hierarchies of power, anger rumination likely has a less significant role than other factors (Steiner and Woolredge, 2009).

Also, our results highlight that the indirect pathway from trait mindfulness to aggression (via anger rumination) carries a stronger predictive weight than the direct effect of trait mindfulness alone. Specifically, in the cases of anger, hostility and total aggression, the indirect effects not only reached statistical significance but also exceeded the size of the corresponding direct effects. This pattern suggests that mindfulness operates on these emotional dimensions primarily by reducing ruminative processes, which are in turn key drivers of aggressive behaviour. As such, the mediating role of anger rumination constitutes a central mechanism, and one of the most robust findings of the present study.

Among the limitations of the present study is that the study design being correlational, which prevented us from establishing definitive causal relationships. In this sense, it is possible that individuals with lower levels of aggression or anger rumination may be more likely to report higher levels of mindfulness, rather than inverse. Clarifying the directionality of these associations remains an important goal for future studies. So, future research could benefit from the use of experimental or longitudinal designs to more accurately explore the relationships between trait mindfulness, anger rumination and aggression. A further limitation is that all the variables were measured by means of self-report instruments, which could be subject to biases such as social desirability as well as the participants’ ability to accurately assess their own levels of trait mindfulness, anger rumination, or aggression. Thus, including third-party reporting might be of interest in future studies. In addition, the involvement of a prison officer in supporting the data collection process may have influenced participants’ responses, potentially increasing social desirability bias. Although the cognitive mechanisms linking mindfulness and anger rumination may operate similarly across settings, cultural norms and institutional factors can shape the expression of aggression. As the sample was limited to a single correctional facility, future research should replicate these findings across diverse national and institutional contexts. Moreover, the lack of qualitative data limited our understanding of participants’ subjective experiences. Including qualitative approaches in future studies could provide deeper insight into the psychological and contextual processes involved. Finally, we did not control for the possible impact of other confounding variables that may have influenced the associations established, such as the level of anxiety, depression or stress, as well as other possible factors related to the participants’ social or family environment. It would be advisable for future studies to include these variables to ensure that the effects found are not mediated or influenced by such psychological or contextual variables.

Conclusions

Aggressive behaviours may be a problem for both co-existence in prison and for inmates’ subsequent rehabilitation and social reintegration. In this sense, our results provide empirical evidence supporting the idea that anger rumination is a key mechanism in maintaining high levels of aggression, but that, on the other hand, trait mindfulness may help reduce hostility, anger and levels of overall aggression. More specifically, our findings indicate that anger rumination significantly mediates the relationship between trait mindfulness and certain forms of aggression, particularly anger, hostility, and total aggression. Hence, MBIs might benefit prison populations, focusing not only on enhancing this trait but also on reducing the tendency towards anger rumination, which could have a positive impact on the mitigation of aggressive behaviours. This highlights the importance of targeting cognitive mechanisms in intervention strategies and strengthens the theoretical link between dispositional mindfulness and aggression through emotional processes such as rumination.

Supplemental Material

sj-docx-1-euc-10.1177_14773708251409510 - Supplemental material for Mindfulness as a pathway to reducing anger rumination and aggression in male prisoners

Supplemental material, sj-docx-1-euc-10.1177_14773708251409510 for Mindfulness as a pathway to reducing anger rumination and aggression in male prisoners by D Fernández-Pérez, MC Zabala-Baños, M Parra, E García-Morales and JJ Ricarte in European Journal of Criminology

Footnotes

ORCID iDs

MC Zabala-Baños

JJ Ricarte

Ethics approval

This research was approved by the Clinical Research Ethics Committee on medical products of the Toledo Hospital Complex (Spain) with number 567.

Informed consent

All participants in the study voluntarily provided their written informed consent to take part in the study.

Author contributions

D. F. P.: conducted data analysis, interpretations of results, and wrote the manuscript; C. Z. B.: contributed to data collection and critically revised the manuscript; M. P.: provided methodological expertise and reviewed the manuscript; E. G. M.: contributed to data collection; J. J. R.: supervised research process, supported statistical analysis, and reviewed the manuscript.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability

All the individual participant data underlying the results reported in this article are available upon request.

Use of artificial intelligence

No artificial intelligence tools were used in the design, analysis, interpretation, or writing of this study.

Supplemental material

Supplemental material for this article is available online.

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