How Much Nature Should The Doctor Order?

Being in green spaces makes you physically and mentally healthier. But how long do you have to stay out there? And what even counts as nature, anyway?

Doctors and researchers are now realizing that getting outside is more and more important to our physical, mental, and emotional health. It’s why we flock to beaches, mountains, and forests for vacations—and feel better after (the not working may also help). There is now even an informal term—"nature deficit disorder"—that describes the growing absence of nature in our lives and the damage it does.

But how much nature access do we really need to gain the positive benefits, which include improved mood, reduced allergies, and even lower rates of diseases like cancer and cardiovascular disease? And what is nature really? Will a few manicured athletic fields do, or do we need forests, birds singing, and dew falling?

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This isn’t an abstract question. In the next 30 years, more than 70% of the world’s populations will live in cities, and so humanity’s access to green space may be inherently more confined. City planners and public health officials are working somewhat blind. They know green space is good, but with limited budgets, space, and competing interests, it’s hard to make the case without hard numbers about the extent of public health improvements they might expect from creating a new park, for example.

The problem is that despite more than 30 years of research, scientists don’t know exactly what sort of "dose" of nature we need. Now, some researchers are encouraging the field to shift gears and focus on making practical recommendations.

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"We think it’s time for a new phase of research that really starts to unpick how often, how long for, and what types of nature we need to experience to help improve our health and well-being," says Danielle Shanahan, a postdoctoral research fellow at Australia’s University of Queensland who published a new paper in the journal BioScience on the issue.

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"This kind of information will, of course, help us plan healthier, happier cities. However, it will also help us understand whether ‘nature prescriptions’ could provide an effective treatment for a range of health issues."

These kinds of prescriptions could range from a visit to a secluded forest or simply a view of greenery outside an office window. They could include "green exercise," such as a jog or walk in a park. But how long would you have to exercise to get nature-based improvements? One study done in 2010 showed the greatest mood improvements from green exercise occurred within very short, five-minute periods. So, good news, maybe we only need a short jaunt. Few other studies have been done to answer questions like these.

Shanahan envisions that one day national governments might have guidelines for nature, just like the USDA offers dietary guidelines to improve nutrition today. A doctor, she says, might prescribe a certain number of park visits a week to treat depression or high blood pressure. To get to this point, however, long-term studies and potentially even clinical trials will be needed. "All we need now are field trials that take a close and critical look at what types of nature can help, and how often and for how long we need to visit," she says.