Evidence is building up fast that most people need time in nature to be healthy, both physically and mentally. Although it cannot prove causation, a Finnish study has shown that better health for regular users of nature may cover a broad range of conditions, at least based on the medications they consume. Those who visit parks regularly use fewer drugs, not just for depression and high blood pressure, but anxiety, insomnia, and even asthma, the research suggests.
The evidence for the health benefits of nature has got so strong that doctors in four Canadian provinces are now allowed to give their patients a free ticket to national parks as treatment. Nevertheless, our knowledge of the conditions for which “ecotherapy” works and how to establish optimum doses is sketchy at best.
In an effort to answer these questions, the Academy of Finland and the Ministry of the Environment funded a study, published in Occupational and Environmental Medicine, to see how park exposure affects prescription drug taking.
The study used 16,000 responses to a 2015-16 survey of residents of Helsinki and the neighboring cities of Vantaa and Espoo about their relationship to parks and waterways. The same survey also asked about the use of a variety of prescription medications.
Contrary to some past research, mere proximity to nature, such as being able to see greenery from one’s house, didn’t affect prescription drug use. Nor did the amount of the local area given over to parks, which has been the most frequently studied measure in past studies of this type. However, a strong association was found between how often respondents visited parks and their use of medications.
People who reported visiting parks three to four times a week were 33 percent less likely to use antidepressant and antianxiety medication than those who seldom did. Use of drugs for high blood pressure was 36 percent less likely among the same group. Although the study also included a category for people who visited parks five or more times a week, there was no further reduction in medication use among the most frequent visitors – in some cases they took slightly more drugs than those visiting roughly every second day.
The work complements a recently published study that found Parkinson’s and Alzheimer’s diseases develop more slowly in people who spend time in nature frequently.
One illness that some studies indicate worsens with exposure to nature is asthma, perhaps because pollen is such a common trigger. However, those who visited parks frequently were 26 percent less likely to make use of asthma medication. Then again, it’s possible those most prone to asthma avoid forest bathing, particularly in spring.
As the asthma association indicates, the direction of causality is crucial: do people need lower doses of medications because they spend time in nature, or are the people who are well enough to need less medicine better able to visit their local park? Might there be a third factor, such as exercise, responsible for both measurements?
The authors admit they can’t answer that. We’ll have to hope assessments of interventions like the aforementioned Canadian PaRx trial can. Nevertheless, the authors provided evidence the association holds up after controlling for factors such as socioeconomic status, ruling out some possible explanations.
The paper is published in Occupational & Environmental Medicine.