I always assumed the mental health benefit of being outside came from doing something out there, hiking, running, some kind of movement. A 2025 study out of Harvard T.H. Chan School of Public Health and Stanford’s Natural Capital Project found something that undercuts that assumption almost completely.
The research team pulled together data from 78 separate experimental studies, nearly 5,900 participants total, all either randomized controlled trials or before and after intervention studies, not just surveys asking people to remember how they felt. And the finding that stood out most wasn’t about hiking or forest trails. It was that sitting quietly outside, doing nothing active at all, was more effective at reducing depression than being active in nature. Both were beneficial for things like vitality and mood, but for depression specifically, stillness outperformed movement.
Anne Guerry, co-executive director of the Natural Capital Alliance at Stanford and a co-author on the study, explained the mechanism in a way that finally made sense to me, nature disconnects you from whatever you’ve been stressing about and puts you back in the present moment. That’s easier to do sitting still than it is mid workout, when part of your attention is still on your form, your pace, your breathing.
The study also found urban forests specifically outperformed other types of green space for reducing depression and anxiety, which matters for anyone who assumes you need a real wilderness trip to get any benefit. You don’t. A tree lined city park counts. And young adults, specifically, saw larger benefits than the general population, which is worth knowing given that most mental health disorders first emerge before age 25.
There’s a catch, and it’s one I recognized immediately in my own habits. Researchers found the benefit depends on actually paying attention to what’s around you. Sitting outside while scrolling through your phone doesn’t produce the same effect as sitting outside and genuinely looking at the trees, the light, the sound of wind moving through leaves. The nature has to register, not just exist in the background while your attention stays somewhere else entirely.
As for how much time this actually takes, the numbers I found were smaller and more forgiving than I expected. A separate Harvard T.H. Chan article found measurable benefits from as little as 15 minutes a day, and Finnish researchers cited in a Greater Good Magazine piece put the minimum for lasting effects at around five hours a month, which works out to less than 15 minutes a day averaged out. That’s not a hiking trip. That’s a bench.
I’ve been treating time outside as something to fit in around exercise, a walk that has to also be cardio, a hike that has to also be a workout. The actual research suggests the opposite approach might work better, find a bench, put the phone away, and just sit there being genuinely present for fifteen minutes. No steps required.
Sources. Harvard T.H. Chan School of Public Health and Stanford Natural Capital Project (2025 meta-analysis); Guerry, A., Stanford Natural Capital Alliance.