The U.S. Centers for Disease Control and Prevention’s NHANES report dated April 16, 2025, revealed that the prevalence of depression in the U.S. has increased by 60% over the past decade. Similarly, the 2024 American Psychiatric Association’s annual mental health poll found that 43% of adults felt more anxious than they did in 2023. With the rising incidence of depression and anxiety in society, there is a need to not only understand the causes but also to find ways to mitigate the impact of these two increasingly prevalent challenges to daily well-being.
The recent systematic review and meta-analysis out of the United Kingdom by Wood, Barton, and Wicks1 of research studies focused on the effects of social and therapeutic horticulture on depression and anxiety adds to the evidence that our long relationship with plants can offer a powerful antidote to the challenges of modern life in the 21st century where the majority of the world’s population now lives in urban settings.
However, let us first briefly describe what systematic reviews and meta-analyses are and the scientific contributions they can offer.
Researchers aiming to investigate a specific question, problem, or disease must first define a systematic search strategy to find and identify published research studies on a topic of interest that conform to a predetermined set of specific experimental design characteristics for both exclusion and inclusion, thus creating an initial list of candidate studies.
Typically, multiple qualified scientists carefully evaluate the studies in the initial list, and only those that precisely conform to the predefined systematic search criteria are retained for in-depth review and meta-analysis.
A meta-analysis is a statistical method used to pool and analyze the results from multiple studies, producing a synthesis that can be more statistically robust and dependable than individual studies themselves. Thus, a meta-analysis can demonstrate that a quantitative outcome is more likely to be reproducible when multiple studies are combined within a single analysis. Thereby, meta-analysis plays a role in establishing independent reproducibility in experimentation and findings which are fundamental to the scientific method, supporting discovery, understanding, and application of acquired knowledge.
The researchers identified seventeen quantitative studies of social and therapeutic horticulture focused on depression and/or anxiety through their systematic search and review process which they included in the meta-analysis. The selected studies included four randomized controlled trials, ten quasi-experiments2, and three single-group treatment experiments.
A total of fifteen studies reported outcomes on depression while eight reported on anxiety. Six of the studies reported outcomes for both depression and anxiety. The meta-analysis revealed significant heterogeneity across the studies and the potential for extensive risk of bias for statistical validity. Two main limitations accounting for the potential risk of bias were the inability to blind participants and treatment facilitators and researchers from the treatments being administered and data analyses, and some studies with small sample size being too underpowered to reliably detect true treatment outcomes.
Across the social and therapeutic horticulture studies, the meta-analysis showed large and significant treatment group effect size differences relative to comparator groups for depression and moderate and significant effect size differences for anxiety. The authors suggest the present study is the first to provide evidence of the effectiveness of social and therapeutic horticulture treatments to reduce symptoms in adults with a diagnosis or expressed symptoms of depression and anxiety. Furthermore, the researchers point out that unlike other medical treatment options for depression and/or anxiety, engaging in social and therapeutic horticulture activities also provides simultaneous multiple physical and psychosocial health benefits.
This study adds to the empirical evidence that engaging in horticultural activities can provide substantial health and psychosocial therapeutic benefits.
1Wood, C.J., Barton, J., Wicks, C.L. (2025). Effectiveness of Social and Therapeutic Horticulture for Reducing Symptoms of Depression and Anxiety: A Systematic Review and Meta-analysis. Frontiers in Psychiatry, 15, 1507354. https://doi.org/10.3389/fpsyt.2024.1507354.
2A quasi-experimental design has both a treatment group and comparative group(s), but the study participants are non-randomly assigned to the respective groups. Therefore, the internal validity of the experiment may be lower than that of a randomized controlled trial.
Charles Guy, Emeritus and Courtesy Professor
Department of Environmental Horticulture, University of Florida
Steering Committee, Wilmot Botanical Gardens, University of Florida