Abstract
Nature-based therapy (NBT) has been growing as a therapeutic option and has demonstrated effectiveness in addressing numerous mental health issues. However, many NBT study designs are limited in their external validity because the intervention is complicated and time intensive, appropriate comparison groups are not included, and the effect of nature cannot be isolated. Using Behavioral Activation with Mindfulness exercises, this study uses three treatment conditions (Outdoor, Indoor, Control) to isolate the effect of nature. While taking part in physical activity, participants in the active treatment conditions are taught four mindfulness exercises in either an outdoor or indoor setting. Using linear mixed models analyses, results indicate that the Outdoor condition may have more impact on improvement of depressive symptoms, connectedness to nature, and mindfulness than Indoor and Control. Implications for clinicians and future research directions are discussed.
Introduction
Research indicates that engagement with and access to nature and green space is beneficial to individuals’ mental health (Butler & Friel, 2006; De La Osa et al., 2024; Kotera, Richardson, & Sheffield, 2022; Ryan et al., 2010; Wilson, Ross, Lafferty, & Jones, 2009). Numerous theories and research studies suggest that exposure to nature can relieve stress and enhance cognition (Berman, Jonides, & Kaplan, 2008; Bowler, Buyung-Ali, Knight, & Pullin, 2010; Ulrich et al., 1991). These findings support perspectives from environmental and evolutionary psychology that identify the urban lifestyle removed from nature as a relatively recent development in human history, very different from the environments in which the species evolved (Bowler et al., 2010; Li, Van Vugt, & De Vries, 2020). Within a broader context, theoretical perspectives such as the Biophilia Hypothesis (Wilson, 1984) suggest that humans have an innate draw toward connection to nature and attention restoration theory (Ohly et al., 2016), which explains how natural environments can restore attention and focus. These perspectives offer some framework for why mental health can benefit from exposure to nature. Indeed, research interest in the effects of nature has been consistent and productive and has led to the development of numerous psychological interventions that emphasize and integrate the use of nature in their design.
Nature-based therapy: Effectiveness and challenges
In the past two decades, nature-based therapy (NBT) has been growing steadily within environmental and clinical psychology as a therapeutic option with demonstrated effectiveness in improving mental health (Hyvönen, Salonen, Paakkolanvaara, Väkeväinen, & Korpela, 2023; Kotera et al., 2022; Lovati et al., 2023; Maund et al., 2019; Shin et al., 2013). Research indicates that NBTs can reduce depressive symptoms through a variety of methods, including interventions that integrate mindfulness and relaxation (Muller et al., 2025), restorative experiences (Hyvönen et al., 2023), and exposure to environments such as wetlands (Maund et al., 2019) and forests (Kim, Lim, Chung, & Woo, 2009).
Despite the growth of the evidence base for NBTs, they are often conducted with study designs that limit their external validity. Many NBTs rely upon periods of complex and intense outdoor activity and exposure, often including overnight commitment from researchers and participants (e.g., Bandoroff & Scherer, 1994; Dolgin, 2014). While NBTs with these study designs have demonstrated effectiveness, these interventions are not well-suited for typical clinical settings. As a result, it is difficult to generalize from research involving these types of NBTs, and portability to working clinicians is not immediately clear.
Another challenge that NBTs face is that a majority of this research relies upon including nonequivalent comparison groups or no control group designs (Bettmann, Gillis, Speelman, Parry, & Case, 2016; Muller et al., 2025). Many NBT studies report that the intervention being utilized appears to be effective at improving treatment outcomes. However, it is difficult to interpret what the effect of nature is because including a comparison group that receives an equivalent “dose” of an NBT while isolating or removing the nature component is often difficult and impractical. Thus, it remains generally unknown whether an NBT’s effectiveness is driven by an individual’s exposure or access to nature. This study aimed to address these common methodological issues in NBT methodological design.
Current study foundation
Behavioral activation
The present study design relies on two primary intervention techniques: Behavioral Activation (BA) and mindfulness. BA is an empirically supported, third-wave cognitive-behavioral approach that has been shown to be effective in improving depression and anxiety (Cuijpers, van Straten, & Warmerdam, 2007; Stein, Carl, Cuijpers, Karyotaki, & Smits, 2021). BA utilizes operant conditioning to improve mood by directing participants to engage in positive, meaningful, and enjoyable activities. As individuals learn to involve themselves in reinforcing activities, they can find themselves breaking out of maladaptive behavioral patterns that are associated with depression and anxiety. This in turn can lead to improvements in mood.
In this study, the reinforcing behavior we attempt to increase is mild-to-moderate physical activity through walking/hiking. Research indicates that exercise itself has been found to benefit mental health and improve depressive and anxious symptoms (see Strohle, 2009) and that physical activity can be effectively utilized in BA practices (Lejuez, Hopko, & Hopko, 2001; Martell, Dimidjian, & Herman-Dunn, 2021).
Mindfulness
Mindfulness is the other primary intervention technique used in the present study. The definition of mindfulness is “the awareness that emerges through paying attention on purpose, in the present moment, and nonjudgmentally to the unfolding of experience moment by moment” (Kabat-Zinn, 2003, p.145). Mindfulness-based interventions (MBIs) have been shown to reduce anxiety, depression, and stress (Hofmann, Sawyer, Witt, & Oh, 2010; Hofmann & Gómez, 2017; Sharma & Rush, 2014). In addition, MBIs have demonstrated effectiveness in improving well-being (Lomas, Medina, Ivtzan, Rupprecht, & Eiroa-Orosa, 2019), connectedness to nature (Howell, Dopko, Passmore, & Buro, 2011), post-traumatic stress disorder (Boyd, Lanius, & McKinnon, 2018), anger (Borders, Earleywine, & Jajodia, 2010), and impulsivity (Franco, Amutio, López-González, Oriol, & Martínez-Taboada, 2016). Overall, mindfulness approaches to mental health are well-validated and complementary to BA for the purposes of this study’s design.
Behavioral activation with mindfulness
Knowing the foundational assets and empirical effectiveness of both BA and mindfulness, this intervention uses these strengths in combination because of the unique characteristics that can be utilized to address the challenges that face some NBTs. Recent research on the combination of Behavioral Activation with Mindfulness (BAM) has been shown to be specifically effective at improving depressive symptoms (McIndoo, File, Preddy, Clark, & Hopko, 2016; Sun, Wong, Zhang, Chen, & Yip, 2021; Wong et al., 2018). These BAM interventions have demonstrated effectiveness while also being time-limited and portable to working clinicians.
Aims of the current study
To address the major concerns in the previous NBT methodology, we aimed to design treatment conditions where we could isolate the effect of nature as the target independent variable. As such, two conditions (Outdoor and Indoor) have active interventions that utilize BAM techniques. This design will allow us to better examine the effect of nature on the study’s dependent variables. Individuals in active treatment conditions participated in two time-limited treatment sessions to address the issue of treatment portability and utilization for more traditional clinical practitioners.
We hypothesized that both active treatment conditions would lead to better outcomes (e.g., depression, anxiety, connectedness to nature, mindfulness) compared with the Control condition. Moreover, we hypothesized that the effect of nature in the Outdoor condition would lead to superior outcomes above and beyond those of the Indoor condition.
Methods
Participants and screening
Participants were recruited through in-person courses, email announcements, and fliers at a public university in the southwest United States. Potential participants were directed to an online screening questionnaire to determine if they met the other inclusion criteria: (1) 18 years of age or older, (2) score of 14 or more on the Beck Depression Inventory-II (BDI-II; Beck, Steer, & Brown, 1996), and (3) did not endorse a 2 or higher on the BDI Suicidality item (e.g., 2—I would like to kill myself, 3—I would kill myself if I had the chance). Among 81 individuals who did not meet inclusion criteria, 76 individuals had a score of less than 14 on the BDI, 4 endorsed a 2 or higher on the Suicidality item, and 1 was under the age of 18. As per the study’s safety plan, the four individuals who did not meet the inclusion criteria due to the Suicidality item were contacted via email and provided with information about available local, online, and telehealth mental health resources. As this study was exploratory in nature, no a priori power analysis was conducted. Sample size was determined based on feasibility and available resources. Figure 1 details the recruitment and enrollment of participants.
Recruitment and enrollment.
Thirty-one individuals participated in the study with an average age of 20.7 years. Fifteen identified as female (48.39%), 13 as male (41.94%), and 3 as transgender and/or genderfluid (9.68%). For participants’ ethnicity, 16 participants identified as Hispanic or Latina/o/x (51.61%), 16 as White (51.61%), 3 as Black (9.68%), 2 as First Nations/Native American (6.45%), 1 as Middle Eastern (3.23%), and 1 as two or more races (3.27%). Percentages do not total 100% as participants were able to choose more than one ethnicity. All individuals gave written informed consent to participate in this study, which was reviewed and approved by the authors’ university institutional review board (Approval Number #005-2023). Informed consent materials indicated that the study examined the effects of physical activity on mood, but did not disclose the primary independent variable: condition type (e.g., Outdoor, Indoor, Control). All participants were debriefed after completion of the study.
The compensation structure for this study was twofold. First, if participants completed questionnaires at all three follow-up time points, they were compensated with a $50 gift card. Second, for every completed study questionnaire, they earned an entry into a drawing for a $100 gift card that was distributed at the completion of data collection.
Measures
Depressive symptoms
Depressive symptoms were measured using the BDI. The BDI is a self-report, 21-item measure using a 0–3 scale. The BDI assesses several domains of depression, including sadness, guilt, suicidality, and changes in appetite and sleep. It has shown good convergent, divergent, and construct validity (Segal, Coolidge, Cahill, & O’Riley, 2008). Prior research shows good internal consistency for the BDI (α = 0.90) (Segal et al., 2008; Steer, Rissmiller, & Beck, 2000), and for this study, Cronbach’s alpha was good at T1 (α = 0.86) and excellent at T2 (α = 0.95) and T3 (α = 95).
Anxious symptoms
The State-Trait Anxiety Inventory (STAI) was used to measure trait and state levels of anxiety (Spielberger, Gorsuch, Lushene, Vagg, & Jacobs, 1983). Example items are “I am tense” and “I worry too much over something that really doesn’t matter.” All 40 inventory items use a 4-point scale (“Almost Never” to “Almost Always”) with higher total scores indicating higher levels of anxiety. The STAI has demonstrated good internal consistency, test–retest reliability, construct, and convergent validity (Spielberger et al., 1983). Cronbach’s alpha for this sample was acceptable at T1 (α = 0.85) and T3 (α = 0.70), but poor at T2 (α = 0.53). T2 results of this measure should be interpreted with caution.
Nature
The Connectedness to Nature Scale (CNS) is a 14-item questionnaire that assesses respondents’ trait levels of feeling connected to nature (Mayer & Frantz, 2004). It utilizes a 5-point scale (“strongly disagree” to “strongly agree”). Sample items include “I often feel a sense of oneness with the natural world around me” and “I often feel part of the web of life.” The CNS has strong test–retest reliability, internal consistency, and scale items load on a single factor (Mayer & Frantz, 2004). Additional evidence has been found of the CNS’s convergent, divergent, and predictive validity (Lovati et al., 2023). Cronbach’s alpha for this sample was good at T1 (α = 0.82), T2 (α = 0.78), and T3 (α = 0.86).
Mindfulness
The Mindful Attention Awareness Scale (MAAS) measures the presence of mindful states in an individual (Brown & Ryan, 2003). This 15-item scale uses a six-point Likert scale (“almost always” to “almost never”) and has sample items such as “I find it difficult to stay focused on what’s happening in the present” and “I find myself doing things without paying attention.” It has demonstrated construct, criterion, convergent, discriminant, and incremental validity as well as good test–retest reliability (Brown & Ryan, 2003; Carlson & Brown, 2005). Cronbach’s alpha for this sample was excellent at T1 (α = 0.90), T2 (α = 0.93), and T3 (α = 0.91).
Demographics
Information about participants’ age, gender identity, and ethnicity was collected.
Design
The study followed a 3 (condition: Outdoor, Indoor, Control) × 3 (time: pretreatment [T1], one-week post-treatment [T2], one-month follow-up [T3]) factorial design, with 31 participants randomly assigned to conditions using computer-generated randomization (see Fig. 1). The online T2 follow-up occurred approximately 1 week after completion of the Outdoor/Indoor sessions for the Outdoor and Indoor conditions (e.g., approximately 3 weeks after T1). The Control condition was asked to complete the T2 follow-up approximately 3 weeks after completing T1. The online T3 follow-up occurred approximately 1 month after T2.
At T1, the Outdoor condition had 11 participants, the Indoor and Control conditions each had 10. T2 had 11 Outdoor, 10 Indoor, and 9 Control participants. T3 had 10 responding participants in each condition.
Procedure
Treatment conditions
The three study conditions fell into two categories as follows: active and nonactive. The two active conditions were Outdoor and Indoor with the nonactive condition being the Control.
Active conditions
Participants in both active conditions participated in two BAM sessions as individuals. These sessions lasted approximately 50 min and were scheduled at least 1 week apart. In each session, mindfulness exercises were taught and practiced while maintaining a comfortable walking pace or while sitting comfortably after walking. In general, the selected exercises have been drawn and/or adapted from Mindfulness-Based Stress Reduction techniques (Kabat-Zinn, 2003; Kabat-Zinn & Hanh, 2013).
Mindfulness exercises
The Five Senses
This exercise (also referred to as 5-4-3-2-1) aimed for individuals to direct their attention to their current environment by engaging in their five senses (e.g., sight, touch, sound, smell, taste). The study therapist would first ask participants to identify five things that they could see (e.g., the different shades of blue in the sky, the blooming flowers along the path), followed by four things they could feel (e.g., the breeze in their hair), three things they could hear (e.g., birds chirping, people bouncing balls), two things they could smell (e.g., flowers, other flora), and one thing they could taste (e.g., water, candy). By focusing on these senses, individuals can more easily focus on the present moment while potentially moving away from anxious thoughts. This was the first exercise introduced during the first session.
Body Scan
This exercise taught participants to focus on different areas of the body to help with awareness, relaxation, and grounding. Participants were guided to notice feelings and sensations starting in their feet and progressing to the top of their heads. This was the second exercise of the first session and was introduced after approximately 20 min of walking and while participants were sitting comfortably. After learning Body Scan while still, the participant resumed walking while being directed through the Body Scan script again, and noticing the differences in the body from a still to active state.
Mindful Walking
This was the first exercise of the second session, which shares elements of the Five Senses and Body Scan exercises and extends those lessons. While walking at a normal pace, participants were directed to bring their attention to the sights, sounds, and other sensory experiences going on around them. In addition, they were encouraged to attend to any physical sensations they were experiencing in their bodies.
Mindfulness of Breath
The last exercise of the second session was also conducted while sitting comfortably. The Mindfulness of Breath exercise is simultaneously straightforward and complex, as participants were guided to simply focus on their breath. With every inhale and exhale, they were instructed to attend to the sensations and experience of breathing, thus aiding in grounding to the present moment. If their attention wandered during the exercise (as they were told that it typically does), they were instructed to gently acknowledge that their focus had shifted and return to the breath. This exercise was guided while sitting still for approximately 5 min and then practiced by participants while resuming walking.
At the end of the second session, participants were thanked and informed that online follow-up surveys would be sent out to them in 1 week (T2) and, after that, 1 month later (T3). All sessions took place during daylight hours.
Outdoor condition
The Outdoor condition sessions took place on a one-and-a-half-mile paved path that ran along a small stream. Along the path were a large variety of trees and other greenery. At the midway point, the participant and therapist would cross a small bridge that led to a clearing that had a stone lectern surrounded by wooden seating. This was the location where the exercises that were best introduced while sitting still were conducted (e.g., Body Scan, Mindfulness of Breath) before resuming the walk.
Outdoor sessions were only conducted when the weather was determined to be suitable for outdoor activities. Sessions were scheduled between late August and mid-November and between mid-February and early April. The range of temperatures for Outdoor sessions was between 61 and 82 degrees Fahrenheit (16°C and 27°C) with little to no precipitation. No Outdoor sessions were canceled due to inclement weather.
Indoor condition
All Indoor condition sessions took place inside a large university gymnasium during the same date range and times as the Outdoor condition. The indoor space was well-lit and air-conditioned. The gymnasium was equipped with an elevated walking track that encircled a full-sized basketball court. The walking track was where most of the physical activity took place. When the still exercises were introduced, participants were led to a classroom adjacent to the basketball court. There, the exercises could be introduced and practiced in relative quiet. Then, continued practice and physical activity were resumed on the walking track, like the Outdoor condition.
Control condition
Participants randomized to the Control condition were informed that they had been enrolled in the study and that online follow-up surveys would be sent to them in approximately 3 weeks (T2) and, subsequently, 1 month after that (T3). After completion of their T3 survey, all Control participants were offered the BAM intervention in either an outdoor or indoor setting. No Control participants chose to participate in the BAM intervention offer.
Therapist training
D.P. is a licensed clinical psychologist and served as a study therapist. In addition, two other study therapists were trained by D.P. Both were master’s level clinical psychology/counseling graduate students and were trained in the active treatment condition procedures during a series of discussions and training sessions. Through check-ins and supervision, D.P. continually assessed treatment fidelity of the additional study therapists.
Results
For data analysis, we conducted linear mixed models using JASP version 0.95.3 (2025). To assess demographic comparability of groups at T1, age and gender were compared across treatment conditions. Age did not significantly differ, and gender distribution was similar across groups.
Assumptions
Skewness and kurtosis were found to be within an acceptable range for most outcome variables, indicating that the data could be well modeled by a normal distribution. T1 and T3 STAI-State and T1 STAI-Trait showed marked positive kurtosis and negative skewness. Although linear mixed models are relatively robust to these characteristics, results with these variables should be interpreted with caution. Levene’s test for homoscedasticity did not reveal any significant results. Examination of residual diagnostics, including residual-versus-predicted plots, QQ plots, and histograms, indicated that assumptions of normality and independence of residuals had been reasonably met.
Main analyses
Linear mixed models were used to examine the effect of time (pretreatment [T1], 1-week follow-up [T2], and 1-month follow-up [T3]) and treatment condition (Outdoor, Indoor, Control) on the outcome variables. Both time and treatment condition were used as fixed effects variables. Participants were entered as random effects to account for repeated measurements. Table 1 displays the estimated marginal means and standard errors for each outcome variable at three time points.
Estimated Marginal Means and Standard Error for Study Outcome Variables From the Linear Mixed Model at Pretreatment (T1), 1-Week (T2), and 1-Month (T3) Follow-Up
BDI, Beck Depression Inventory; CNS, Connectedness to Nature Scale; MAAS, Mindful Attention Awareness Scale; SE, standard error; STAI, State-Trait Anxiety Inventory; T1, Time 1; T2, Time 2; T3, Time 3.
For the BDI, a significant main effect of time was found, F(2, 54.50) = 29.87, p < 0.001. In addition, a significant Time × Condition interaction was found, F(4, 54.49) = 3.21, p < 0.02. Estimated marginal means pairwise contrasts (Holm-adjusted) indicate that at T2, the Outdoor condition (M = 9.91, standard error [SE] = 3.32) was significantly lower compared with Control (M = 22.50, SE = 3.58), z = −2.58, 95% confidence interval (CI) [−22.16, −3.02], p_Holm = 0.03. At T3, BDI scores for both the Outdoor condition (M = 8.59, SE = 3.41), z = −2.59, 95% CI [−22.16, −3.07], p_Holm = 0.03 and Indoor condition (M = 9.20, SE = 3.48), z = −2.44, 95% CI [−21.65, −2.35], p_Holm = 0.03 were significantly lower than Control (M = 21.20, SE = 3.41). Figure 2 displays the estimated marginal means from the linear mixed model across each time point by treatment condition.
Estimated marginal means of BDI by treatment condition across time. Error bars represent ±1 SE of the mean. BDI, Beck Depression Inventory; SE, standard error.
For the MAAS, marginally significant results were found at T2. MAAS scores for the Outdoor condition (M = 63.00, SE = 4.23) were higher compared with Indoor (M = 49.40, SE = 4.44), z = 2.22, 95% CI [1.574, 25.63], p_Holm = 0.053 and Control (M = 48.21, SE = 4.55), z = 2.38, 95% CI [2.61, 26.97], p_Holm = 0.052 (Fig. 3). No other significant or marginally significant results were found for other outcome variables and time points.
Estimated marginal means of MAAS by treatment condition across time. Error bars represent ±1 SE of the mean. MAAS, Mindfulness Attention Awareness Scale; SE, standard error.
To examine within-subject changes over time by treatment condition, pairwise comparisons of estimated marginal means were conducted within each condition, with Holm-adjusted p-scores used to control for Type I error. For the BDI, participants in the Outdoor condition had significant reductions from T1 (M = 24.73, SE = 3.32) to T2 (M = 9.91, SE = 3.32), z = 5.10, 95% CI [9.12, 20.52], p_Holm < 0.001 and T3 (M = 8.59, SE = 3.41), z = 5.37, 95% CI [10.25, 22.03], p_Holm < 0.001. Similarly, the Indoor condition had significant reductions from T1 (M = 26.80, SE 3.48) to T2 (M = 17.40, SE = 3.48), z = 3.08, 95% CI [3.42, 15.38], p_Holm = 0.006 and T3 (M = 9.20, SE 3.48), z = 5.77, 95% CI [11.62, 23.58], p_Holm < 0.001. No significant changes were found for the Control group as a function of time.
Within-subject changes over time for other outcome variables were seen for the MAAS and CNS only among the Outdoor conditions. For the MAAS, there was a significant increase from T1 (M = 52.18, SE = 4.23) to T2 (M = 63.00, SE = 4.23), z = −3.19, 95% CI [−17.46, −4.18], p_Holm = 0.008. Significant increases in CNS scores were seen from T1 (M = 43.18, SE = 2.24) to T2 (M = 48.45, SE = 2.24), z = −3.31, 95% CI [−8.40, −2.15], p_Holm = 0.006 and T3 (M = 47.50, SE = 2.28), z = −2.62, 95% CI [−7.55, −1.08], p_Holm = 0.04 (Fig. 4). No other significant results were found within the other treatment conditions for other outcome variables. Data from this research study are available from the corresponding author, D.P., upon reasonable request.
Estimated marginal means of CNS by treatment condition across time. Error bars represent ±1 SE of the mean. CNS, Connectedness to Nature Scale; SE, standard error.
Discussion
Although significant results were not consistent on outcome variables across conditions and time points, the overall trend supports the effectiveness of exposure to nature in improving depressive symptoms, feelings of connectedness to nature, and mindfulness. For depressive symptoms, we found evidence of improvement among the Outdoor and Indoor conditions compared with Control, but comparisons of estimated marginal means did not find differences between the Outdoors compared with Indoor condition. For changes in mindfulness, we found marginally significant results indicating that the Outdoor condition may increase mindful awareness compared with Indoor and Control conditions. Within-group change did indicate more improvements for the Outdoor and Indoor conditions’ participants on depressive symptoms, but improvements over time on connection to nature and mindfulness were only found for the Outdoor condition.
The findings that the Outdoor condition was particularly effective at reducing depressive symptoms align with previous findings in the NBT literature (Hyvönen et al., 2023; Kim et al., 2009; Maund et al., 2019; Muller et al., 2025). Improvement of depressive symptoms among both active conditions also aligns with previous BA research (Cuijpers et al., 2007; Stein et al., 2021). In addition, for both between- and within-group change, we saw that when significant results were detected, they were primarily found with the Outdoor condition. Furthermore, by isolating the independent variable of exposure to nature across conditions, this study’s design helps contribute to the research base that the effect of nature may uniquely contribute to positive treatment outcomes in NBTs. The present study was able to successfully isolate one other effect of nature, albeit an unsurprising one; participants in the Outdoor condition reported significantly increased feelings of connectedness to nature compared with the Indoor and Control conditions, which is related to existing research showing that exposure to nature improves vitality (Ryan et al., 2010).
The effect of nature can also be seen in participants’ levels of mindfulness. We think this is a particularly interesting finding because both active treatment conditions provide the same training and dedicate the same amount of time to the mindfulness exercises. Yet, between-group differences were only found for the Outdoor condition compared with Indoor and Control, where the Indoor condition was not found to be significantly different from Control. Furthermore, within-group change indicates that the only condition that improved in mindfulness from T1 was the Outdoor, despite being trained on the same exercises in both active treatment conditions. Prior research on mindfulness interventions in nature has found similar results (e.g., Djernis et al., 2019; Shin et al., 2013) with our results adding to this research base, indicating that exposure to nature may help complement or strengthen the effectiveness of mindfulness exercises. Indeed, “context may play a significant role in the benefits of mindfulness-based interventions” (Djernis et al., 2019, p. 14).
Limitations
The primary limitation of this study is the limited sample size. As such, interpretation of these results should be taken with caution, and findings can be considered more preliminary. We believe that these findings are important and interesting results that can be used to further generate hypotheses and research in the field, rather than being considered definitive. With a larger sample size in future studies, there is greater statistical power and less concern for Type II error. In addition, finding no significant differences for any of the anxiety outcomes may be accounted for by the poor reliability and issues with skewness and kurtosis with the STAI, and that depressive symptoms, not anxiety, were used as study inclusion criteria. Future research may want to explore whether using levels of anxiety as the primary inclusion criteria would lead to significant findings. In addition, all outcomes relied on participant self-report, and future research could consider behavioral and/or physiological indicators of change.
Implications for practice and future directions
This research has several strengths, particularly regarding its study design. This specific design is relatively rare in its ability to isolate the unique effect of nature (Kim et al., 2009; Shin et al., 2013) by including an active condition that is not exposed to nature and a nonactive Control condition. In addition, while many NBT studies utilize complex or time-intensive interventions (Bandoroff & Scherer, 1994; Dolgin, 2014), implementation and introduction of BAM exercises may be more portable and accessible to practicing clinicians who cannot practically offer complex NBTs, but still want to take advantage of the psychological effect of nature.
Finally, based on the effects of nature on clinical outcomes in this and previous studies, future research may want to examine whether exposure to nature in clinical settings also positively affects therapeutic process variables such as working alliance, perceived therapist competence and credibility, and session value. Should exposure to nature increase the strength of these clinical process variables, it could have implications for reducing client dropout rates and increasing intervention outcomes and effectiveness.
Authors’ Contributions
D.P.: Conceptualization, funding acquisition, methodology, data analysis, writing—original draft, and review and editing and C.R.: Data collection, writing—original draft, and review and editing.
Footnotes
Author Disclosure Statement
The authors declare no conflicts of interest.
Funding Information
This work was supported by the Faculty Research Committee of New Mexico Highlands University.