Growing Evidence Gardening Cultivates Mental Health

Taking up gardening is linked to improved mood and decreased stress, new research suggests.

The results of the small pilot study add to the growing body of evidence supporting the therapeutic value of gardening, study investigator Charles Guy, PhD, professor emeritus, University of Florida Institute of Food and Agricultural Sciences, in Gainesville, told Medscape Medical News.

“If we can see therapeutic benefits among healthy individuals in a rigorously designed study, where variability was as controlled as you will see in this field, then now is the time to invest in some large-scale multi-institutional studies,” Guy added.

The study was published online July 6 in PLOS ONE.

Horticulture as Therapy

Horticulture therapy involves engaging in gardening and plant-based activities facilitated by a trained therapist. Previous studies found that this intervention reduces apathy and improves cognitive function in some populations.

The current study included healthy, non-smoking and non-drug using women, whose average age was about 32.5 years and whose body mass index was less than 32. The participants had no chronic conditions and were not allergic to pollen or plants.

Virtually all previous studies of therapeutic gardening included participants who had been diagnosed with conditions such as depression, chronic pain, or post-traumatic stress disorder. “If we can see a therapeutic benefit with perfectly healthy people, then this is likely to have a therapeutic effect with whatever clinical population you might be interested in looking at,” said Guy.

In addition, including only women reduced variability, which is important in a small study, he said.

The researchers randomly assigned 20 participants to the gardening intervention and 20 to an art intervention. Each intervention consisted of twice-weekly 60-minute sessions for 4 weeks and a single follow-up session.

The art group was asked not to visit art galleries, museums, arts and crafts events, or art-related websites. Those in the gardening group were told not to visit parks or botanical gardens, not to engage in gardening activities, and not to visit gardening websites.

Activities in both groups involved a similar level of physical, cognitive, and social engagement. Gardeners were taught how to plant seeds and transplant and harvest edible crops, such as tomatoes, beans, and basil. Those in the art group learned papermaking and storytelling through drawing, printmaking, and mixed media collage.

At the beginning and end of the study, participants completed six questionnaires: the Profile of Mood States 2-A (POMS) short form, the Perceived Stress Scale (PSS), the Beck Depression Inventory II (BDI-II), the State- Trait Anxiety Inventory for Adults (STAI) (state anxiety is a temporary feeling or emotion, and trait anxiety is about a personal characteristic), the Satisfaction With Participation in Discretionary Social Activities (SPDSA), and the 36-item Short Form Survey (SF -36).

Participants wearing wrist cuff blood pressure and heart rate monitors.

The analysis included 15 persons in the gardening group and 17 in the art group.

Participants in both interventions improved on several scales. For example, the mean preintervention POMS TMD (T score) for gardeners was 53.1, which was reduced to a mean of 46.9 post intervention (P = .018).In the art group, the means score was 53.5 before the intervention and 47.0 after the intervention (P = .009).

For the PSS, mean scores went from 14.9 to 9.4 (P = .002) for gardening and from 15.8 to 10.0)P = .001) for artmaking.

For the BDI-II, mean scores dropped from 8.2 to 2.8 (P = .001 (for gardening and from 9.0 to 5.1)P = .009) for art.

However, gardening was associated with less trait anxiety than artmaking. “We concluded that both interventions were roughly equally therapeutic, with one glaring exception, and that was with trait anxiety, where the gardening resulted in statistical separation from the art group,” said Guy.

There appeared to be dose responses for total mood disturbance, perceived stress, and depression symptomatology for both gardening and artmaking.

Neither intervention affected heart rate or blood pressure. A larger sample might be needed to detect treatment differences in healthy women, the investigators note.

The therapeutic benefit of gardening may lie in the role of plants in human evolution, during which “we relied on plants for shelter; we relied on them for protection; we relied on them obviously for nutrition,” said Guy.

The study results support carrying out large, well-designed, rigorously designed trials “that will definitively and conclusively demonstrate treatment effects with quantitative descriptions of those treatment effects with respect to dosage,” he said.

Good for the Mind

Commenting for Medscape Medical NewsSir Richard Thompson, MD, past president, Royal College of Physicians, London, UK, who has written about the health benefits of gardening, said this new study provides “more evidence that both gardening and art therapy are good for the mind” with mostly equal benefits for the two interventions.

“A much larger study would be needed to strengthen their case, but it fits in with much of the literature,” said Thompson.

However, he acknowledged the difficulty of carrying out scientifically robust studies in the field of alternative medicine, which “tends to be frowned upon” by some scientists.

Thompson identified some drawbacks of the study. In trying to measure so many parameters, the authors “may have had to resort to complex statistical analyses,” which may have led to some outcome changes being statistically positive by chance.

He noted that the study was small and that the gardening arm was “artificial” in that it was carried out in a greenhouse. “Maybe being outside would have been more beneficial; it would be interesting to test that hypothesis.”

As well, he pointed out initial differences between the two groups, including income and initial blood pressure, but he said he doubts these were significant.

He agreed that changes in cardiovascular parameters wouldn’t be expected in healthy young women, “as there’s little room for improvement.

“I wonder whether more improvement might have been seen in participants who were already suffering from anxiety, depression, etc.”

The study was supported by the Horticulture Research Institute, the Gene and Barbara Batson Endowed Nursery Fund, Florida Nursery Growers and Landscape Association, the Institute of Food and Agricultural Sciences, Wilmot Botanical Gardens, the Center for Arts in Medicine, Health Shands Arts in Medicine , and the Department of Environmental Horticulture at the University of Florida. The authors have disclosed no relevant financial relationships.

PloS One. Published online July 6, 2022. Full text

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