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, Gainesville, told this news organization.
“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,” Dr. Guy added.
The study was published online 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, nonsmoking, 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 PTSD. “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 Dr. 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, the Satisfaction With Participation in Discretionary Social Activities, and the 36-item Short-Form Survey.
Participants wore 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 Dr. 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 noted.
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 Dr. 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.