PULLMAN, Wash. — Flowers and plants given to the ill may do more than just brighten their day. A study of pain perception at Washington State University has found that plants may help reduce physical discomfort as well.
“We found more subjects were willing to keep a hand submerged in ice water for five minutes if they were in a room with plants present than if they were in a room without plants,” said Virginia Lohr, chief author of the study in a story appearing in the fall issue of Connections, the alumni publication of the College of Agriculture and Home Economics.
The WSU study expands research conducted in 1984 by a researcher at the University of Delaware. He found that patients recovering from surgery whose hospital room had a view of trees used fewer pain- relieving drugs than patients whose view was a brick wall.
Lohr, a WSU professor of horticulture, conducted the study with Caroline Pearson-Mims, a research technologist in the horticulture and landscape architecture department.
Forty-nine percent of the subjects tested in a room with common green foliage plants kept their hands in ice water for five minutes, compared with 34 percent of the subjects who were tested in the room with colorful objects instead of plants and 30 percent for subjects tested in the same room without plants or colorful objects.
These results mirror research findings elsewhere, but the WSU researchers can’t explain how plants help. “It appears that visual distraction is part of it, but it is clearly more than that, ” Lohr said.
“I personally think it’s because we as humans have evolved with nature and are part of nature,” Pearson-Mims said. “I think we have an innate reaction to plants that we may or may not be aware of.”
The specific objective of the WSU study was to determine if healthy adults who passively view interior plants could tolerate experimentally-induced physical discomfort longer than adults in settings without plants.
A windowless office was used for the experiment. To test the hypothesis, plants or visually stimulating items, including an abstract art poster and a wood and brass weather station, were added or removed.
Of the 198 adults who took part in the double blind study, 69 participated in the plants treatment, 67 in the control treatment, and 62 in the visually stimulating objects treatment.
Each subject was randomly assigned to one treatment and tested individually. After entering the room, they filled out questionnaires to gather background information, determine how they felt about the room and to measure their emotional states. Physiological responses were monitored by recording blood pressure and skin temperature.
Subjects were then asked to place their non-dominant hand in a warm-water bath to make certain that all subjects’ hands were at a similar temperature before placing them in ice water, a common method used to study discomfort.
They were told that they could remove their hands at any time with the length of immersion limited to five minutes for the comfort of the subjects and to prevent their hands from becoming numb. They were not told of the five-minute time limit.
Background information showed no significant differences among subjects in the treatment groups that could be useful in explaining the results of the experiment. Measurements of blood pressure and skin temperature also yielded no useful information.
The room assessment, which was designed to evaluate a subject’s first impressions of the experimental space, and the emotional survey, which measured a subject’s feelings, yielded significant differences.
On some items, subjects rated the rooms with plants and colorful objects as roughly equal in terms of visual interest, grading both as more “interesting, colorful, and ornate” than the control room. This showed that the colorful objects that the researchers placed in the room were visually comparable to the plants.
On other features, the room with plants was rated more positively than either of the other two rooms. The plant room was rated higher on positive contributions of plants, including “fresh air” and “calming,” and subjects felt less fearful when the plants were present.
“Our research confirms previous studies on the stress-reducing benefits of viewing plants,” Lohr said, “and clearly shows that plants contribute more than just visual distraction. More importantly, it shows that the presence of plants can help people tolerate short-term pain.”
The study was funded by the American Floral Endowment and approved by the WSU Institutional Review Board.
Editors: For additional comments, you can reach Dr. Virginia Lohr at 509-335-3101 and Caroline Pearson-Mims at 509-335-4295.
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