Are Nature-assisted Interventions Cost-effective?

Are Nature-assisted Interventions Cost-effective?

By: William C. Young

A review of:
Währborg, P., Petersson, I. F., & Grahn, P. (2014). Nature-assisted rehabilitation for reactions to severe stress and/or depression in a rehabilitation garden: Long-term follow-up including comparisons with a matched population-based reference cohort. Journal of Rehabilitation Medicine, 46(3), 271-276.

Severe stress and depression have become more common and more costly in all populations across the world. Until recently, many of these disorders were going undiagnosed. As the accuracy of diagnosis rises, the accuracy with which we can determine the financial and health-related costs of these disorders also increases. These disorders not only influence the individuals with the disorders but also the businesses or workplaces where they are employed (Gustavsson et al, 2010). Because there is only a marginal effect of most interventions on severe stress and interventions and a high effect of nature assisted interventions, Wahrborg and colleagues (2014) set out to examine if nature-assisted interventions were both therapeutic and cost-effective. Moreover, since there was a small number of studies that had examined the effects of a rehabilitation program versus controls, the study could examine the effect of the intervention in a way that had not been conclusively addressed by prior research.
Wahrborg and colleagues (2014) performed a study in an attempt to determine the effect of nature-assisted interventions on those who are dealing with severe stress and depression. Sick leave status and healthcare consumption were used as dependent variables in an attempt to operationalize a monetary effect of the nature-assisted intervention as well as the overall therapeutic effect. A retrospective, between-subjects design with a matched reference group was used which consisted of an experimental group (nature-assisted rehabilitation program group) and a control group from Skane Health Register.
A nature-assisted intervention was chosen due to high effect sizes shown in similar studies despite lower sample sizes. The intervention (experimental group: N=103) involved both horticulture therapy and medication. The intervention condition was conducted in a green setting which had been proven to be restorative (Annerstedt & Wahrborg, 2011). The methods used in the intervention condition are based on supportive environment theory. The research team hoped to capitalize on therapeutic advantages such as spiritual connection/attachment with nature, natural physical activity, meaningful activities, and an enriched and secure environment (Grahn et al., 2010).
The researchers attempted to use 8 control group participants per case in an attempt to best match the experimental sample by recruiting these individuals from the Skane Health Register. Eventually, 678 participants were recruited as part of the control group spanning from 2000 to 2009. Treatment as usual was employed for those in this control condition.
Ultimately, Wahrborg and colleagues (2014) found that there was a significant reduction in healthcare consumption when the nature-assisted therapy was employed. There was no significant difference in sick leave status. These findings led the research team to conclude that the intervention demonstrated a positive monetary and therapeutic effect.
There were many strengths that other studies in the field should strive to replicate. First, the sample size was high which provided a more accurate depiction of the response of the population to the intervention. Moreover, a large control group was used in an attempt to more closely match the characteristics of the intervention group. In terms of demographic variables, the groups were not significantly different. Also, the research team used multiple outcome measures to examine the monetary effect of their intervention which allowed them to examine multiple aspects of their monetary and psychological variables. Next, the research team used multiple means of analyses to examine the data (chi square, Welch’s t, and ANOVA). These comparisons allowed the research team to determine if there were any differences between the intervention group and the control group. Another strength of the study was that the intervention was backed by strong scientific and theoretical evidence of success. The description of the intervention presented by the authors makes replication of the study more feasible. In addition, the authors analyzed the implications of the results and presented them clearly. These implications did a remarkable job of demonstrating the importance of the research. Lastly, diagnosis of the disorders in the sample was confirmed by an independent psychiatrist. This ensured that participants were in the correct groups and still had the symptoms required to be involved in the study.
While this study had numerous strengths, there were also several limitations and confounds. First, the study sample was not comparable in terms of disorders. Cases could not be matched in terms of symptoms and degree of distress. Therefore, effect of interventions may be influenced by degree of initial symptoms and regression to the mean. Further complicating matters is that the control group reported a higher use of medical care on average before the study began which could account for a portion of the significant findings. Also, there were many different main groups based on disorders. The reported effects are for the overall populations. However, only 27 individuals actually had the main condition (mild to moderate depression). The breakdown of the sample used based on disorders was confusing and difficult to replicate. Another issue with group similarity is that more healthcare contact took place in the experimental condition. This effect could have led to a significant effect on future healthcare and leave use. In addition, the outcome variables may have been confounded by other mediating effects. The significant results may not occur if individuals are likely to catastrophize their pain or not adhere to their medication. Lastly, the sample was recruited from one site which diminishes generalizability. This diminished effect is more noticeable since this article indicated that it is the first to use this intervention. Overall, there is a need for replication to understand how much must change to determine the effectiveness of nature-assisted therapy in a rehabilitation program.
In conclusion, the results demonstrate hope for nature-assisted therapy in rehabilitation settings. However, the outcome measures and samples used may not allow the field to draw any generalizable conclusions. Replications of the intervention methods used while using more settings and more matched populations may lead to results that can allow the field to determine if nature-assisted interventions demonstrate positive therapeutic and monetary effects in rehabilitation settings.


Annerstedt, M., & Währborg, P. (2011). Nature-assisted therapy: Systematic review of controlled and observational studies. Scandinavian Journal of Public Health, 39, 371-388.

Grahn P, Tenngart Ivarsson C, Stigsdotter U, & Bengtsson IL. (2010). Using affordances as a health promoting tool in a therapeutic garden. In Ward Thompson C, Aspinall P, Bell S (Eds.), Innovative approaches to researching landscape and health (pp. 116-154). New York: Routledge.

Gustavsson, A., Svensson, M., Jacobi, F., Allgulander, C., Alonso, J., Beghi, E., … & CDBE2010 Study Group. (2011). Cost of disorders of the brain in Europe 2010. European Neuropsychopharmacology, 21(10), 718-779.

Währborg, P., Petersson, I. F., & Grahn, P. (2014). Nature-assisted rehabilitation for reactions to severe stress and/or depression in a rehabilitation garden: Long-term follow-up including comparisons with a matched population-based reference cohort. Journal of Rehabilitation Medicine, 46(3), 271-276.

To cite this review, please use this reference:
Young, W.C. (2015). Are nature-assisted interventions cost-effective? Psychology Alert (1).