Four weeks of gardening improves mood and reduces depressive symptoms among healthy women

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New findings published in the journal PLOS One add to a body of research supporting the therapeutic benefits of horticultural therapy and art therapy. Healthy women who participated in eight group-based gardening or art-making sessions showed measurable improvements in mood and a reduction in depressive symptoms.

Throughout history, humans have maintained a strong connection to plants and nature. Humans have relied on plants for survival, and some scholars believe that our attachment to nature has evolved through millions of years of evolution. But with increasing urbanization, city dwellers have fewer opportunities to interact with nature. One way for these populations to remain connected to nature is to visit public gardens or take up gardening.

Gardening is suspected to offer therapeutic benefits. For instance, a form of treatment called horticultural therapy uses therapist-guided gardening activities and individual treatment plants to improve mental health. Study author Charles L. Guy and his colleagues wanted to extend the research on the physical and mental health benefits of gardening with a controlled experiment comparing a gardening intervention to another therapeutic activity — art-making. The researchers wanted to explore whether the two types of interventions would offer distinct psychological benefits.

“There is an extensive history and literature of anecdotal endorsements that engaging in gardening activities and horticultural therapy or people-plant interactions such as visiting gardens has therapeutic benefits, particularly with respect to stress, emotions, anxiety, and overall mental well-being,” explained Guy, an emeritus and courtesy professor of plant physiology and biochemistry at the University of Florida.

“What is fundamentally different than most other anecdotal accounts of something having therapeutic properties is the fact that perhaps millions of gardeners have expressed such sentiments for long periods of time. What seems to be presently missing is evidence from properly designed and properly controlled large-scale clinical trials that quantitatively measure treatment effects and outcomes and dosage levels of well-defined and standardized treatment regimen(s). To begin moving in the direction to justify large-scale clinical trials, we required preliminary evidence of treatment effects and outcomes with a well-defined participant population in a small-scale study.”

A sample of healthy women in their early thirties was randomly assigned to one of two interventions. In total, 17 participants took part in an art intervention and 15 participants followed an indoor gardening intervention. Both interventions were group-based and included 8 one-hour sessions spread out over four weeks. The art sessions were led by two professional artists, and the gardening sessions were led by a master’s level horticulturist who was trained in therapeutic horticulture.

Before and after the interventions, all participants completed assessments of mood states, perceived stress, depression, and anxiety. The mood states, stress, and depression assessments were additionally completed at intervals throughout the intervention. Finally, measures of heart rate and blood pressure were collected at the beginning and end of each session.

The overall findings suggested that the interventions offered similar mental health benefits. Participants in both the art and gardening groups showed reductions in mood disturbances, perceived stress, and depression symptoms following the interventions. There was some evidence that the gardening group experienced slightly stronger benefits, having shown reductions in the Trait and State subscales of the State-Trait Anxiety Inventory for Adults. Of note, the findings did not reveal any significant improvements in blood pressure or heart rate, although the researchers observed positive trends for the gardening group.

The “results suggest that engaging in gardening or art-making activities as leisure pursuits may have mental health benefits and perhaps fortify general mental health wellbeing. Additional studies are needed to further expand our understanding how large and extensive gardening may benefit one’s mental and physical health,” Guy told PsyPost.

The results also revealed dosage effects for both interventions, where participants’ mental health scores tended to improve with every session. The study authors discuss several explanations for this dosage effect. For one, it could be that participants experienced stronger benefits throughout the intervention as group participants became more familiar with each other and group cohesion increased. Alternatively, it may be that participants’ self-efficacy increased with repeated sessions or that their emotional connection to the plants grew as they continued to care for them.

“When taken together, group-based gardening or art-making can provide quantitatively measurable improvements in healthy women’s psychosocial health status that imply potentially important public health benefits,” Guy and his colleagues write.

Limitations to the study include a small sample size that consisted only of healthy women, such that the findings cannot be generalized to men or to the wider population of women. Additionally, there was no inactive control group to be compared with the art and gardening intervention groups.

T”here are caveats with our study that were intentionally built into its experimental design and that impact its findings,” Guy explained. “First and foremost, it’s a small study that needs to be confirmed and validated by follow-up large-scale studies. Second, our study population was healthy women ages 26-49. Future studies will need to focus on a general population and then subsequent studies will need to focus on a range of specific clinical populations to see which might benefit and by how much.”

“It is our hope that our study could be a model for future studies where complex treatments can be well-defined, highly structured, and standardized, and outcome assessments can utilize the same methodology and instruments so that studies can be repeated, and results be comparable across multiple studies.”

The study, “A pilot randomized controlled trial of group-based indoor gardening and art activities demonstrates therapeutic benefits to healthy women”, was authored by Raymond Odeh, Elizabeth R. M. Diehl, Sara Jo Nixon, C. Craig Tisher, Dylan Klempner, Jill K. Sonke, Thomas A. Colquhoun, Qian Li, Maria Espinosa, Dianela Perdomo, Kaylee Rosario, Hannah Terzi, and Charles L. Guy.