If you think about it, humans kind of invented “outdoors.” For our primitive ancestors, who roamed entire continents as their sole occupation, makeshift shelter was welcome respite. But now that we’ve vacuum-packed ourselves inside tiny cubes with artificial light, our brains compel us to venture back out, lest they fall to depression and other mental woes.

Heaps of academic research have approached a causal link between nature and mental well-being for years. The more time we spend outside, the better we feel. Now, a new large-scale study from the University of Michigan all but cements the idea, as researchers studying the effects of group nature walks have found people can cut their depression severity and reduce their stress just by going for a stroll.

“We hear people say they feel better after a walk or going outside but there haven’t been many studies of this large size to support the conclusion that these behaviors actually improve your mental health and well-being,” said senior author and associate professor of family medicine Dr. Sara Warber in a statement.

Warber and her colleagues collected data on 1,991 members of the Walking for Health Program in England, which helps coordinate nearly 3,000 weekly walks for 70,000 people a year. Subjects were split evenly among non-walking groups and those taking regular group walks. Both groups were statistically matched using propensity score matching, meaning, in effect, if the team were to find any link it’d be as close to causal as possible.

Not only did the findings show reduced depression symptoms and lower stress levels, but they also indicated jumps in positive mental well-being. The walks weren’t just making people less sad, in other words; they were actually making people happier. For Warber, this could mean a supremely efficient way of raising the national standard of living.

“Group walks in local natural environments may make a potentially important contribution to public health and be beneficial in helping people cope with stress and experience improved emotions,” she said.

The last several years have seen a boon in research into nature’s healing properties. Consider the 2007 study that found dirt particles could have the same positive effect as the common antidepressant Prozac. Or there’s the 2012 study that found taking a walk in the park for an hour could help improve people’s memory and cut their symptoms of Major Depressive Disorder — the grandfather illness in the general category of depressive illness.

These studies, including the latest, are important because they address two major social changes in one fell swoop: urban relocation and mental illness. An estimated one in 10 people has suffered a depressive episode in his or her lifetime. And as the country industrializes, people leave suburbia for the nearest city. Obesity is also a challenge, as the latest data show 34.9 percent of the U.S. is overweight.

Walking, in its simple and timeless beauty, could be the remedy. Plus, it’s a solution that involves no pills, prescriptions, or meds — a mode of healing that has all but engulfed the country’s health care system. Where endless scripts have come to dominate the culture, walking comes back to claim its place.

“Walking is an inexpensive, low-risk, and accessible form of exercise,” Warber said. “And it turns out that combined with nature and group settings, it may be a very powerful, under-utilized stress buster.”

Source: Marselle M, Irvine K, Warber Sara. Examining Group Walks in Nature and Multiple Aspects of Well-Being: A Large-Scale Study. Ecopsychology. 2014.