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It's probably no surprise that nature is beneficial to our mental health. From hitting the beach, to taking a long stroll through the park, multiple studies have shown that there's something about nature that helps us feel happier, more focused, or just generally better.

But why that happens is trickier to figure out. From what psychologists can tell, though, it's not just about getting in some sunshine and Vitamin D. Instead, it might have to do with our sense of belonging.

The idea that nature is healing isn't a new one, and exposure to natural environments has been an important part of mental health treatments for a long time. As early as the Middle Ages, monasteries for those with mental illnesses created so-called restorative gardens. And in the 1800s, people designing mental hospitals would try and make sure their buildings were surrounded by acres of natural land.

So far, modern research really supports this idea, too. Studies have shown that being exposed to nature — whether it's a wilderness preserve or a tree-lined city street — can improve well-being in a bunch of ways, both in those with and without clinical conditions. For example, a 2011 meta-analysis looked at studies involving a total of almost 850 participants — mostly students.

It found that exercising in a natural environment resulted in higher feelings of revitalization than doing the same exercise indoors. And another study from 2012 found that walking through nature for 50 minutes provided a mood boost and other cognitive benefits for twenty participants with depression. There's also evidence to suggest that those with schizophrenia, ADHD, and a whole host of other illnesses experience similar benefits from just taking in a little scenery.

So far, there are several factors that have been floated around as possible explanations for this. One is that nature allows us to recover from stress and attention fatigue. This is the idea that urban environments have too many things competing for our attention.

Other studies suggest that nature offers exercise opportunities, facilitation of social interaction and development, and opportunities for personal development in general. But a lot of these factors haven't been investigated in rigorous depth. They also don't really explain the mechanisms of how we gain psychological benefits just from existing in nature, rather than running around in nature, chilling with friends with nature.

In fact, most research on the subject seems to describe the mechanisms as ‘elusive'. Which is psychologist speak for, “We dunno. We're workin' on it.” Still, that doesn't mean we don't have a hypotheses or two.

Some researchers argue that these positive effects, at least in part, come about because of an increased sense of connectedness to the natural world. One significant experiment about this was published in 2009 in Environment and Behavior, and it looked at the effect of exposure to nature on mood and problem solving. In this study, 76 students were asked to complete questionnaires on mood, along with the Connectedness with Nature Scale – or CNS – which measures pretty much what the name implies.

It asks participants to rate how they feel about some vaguely hippy-ish stuff, like ‘Right now I'm feeling a sense of oneness with the natural world'. Or ‘I'm feeling like the natural world is a community to which I belong'. After rating 13 of those peace and love statements, the students were split into two groups, and bundled onto buses for a field trip.

They took a 20-minute drive to either a nature reserve or a downtown parking lot. Then, they spent around 15 minutes silently walking, sitting, and taking in the scenery before filling out those questionnaires again. The results showed that participants who went to the nature reserve reported significantly more of a mood boost from their trip.

Their feelings of being connected to nature were also higher than those who took a stroll in the parking lot. Now, this in itself isn't massively surprising. You can imagine it's probably hard to feel at one with the universe standing on a stretch of concrete.

What was more interesting is that the CNS survey results seemed to mediate the effects of the environment. More specifically, when people reported that they felt part of nature, their mood boost tended to be bigger. So it wasn't just about seeing nature; it was about feeling like they are part of it.

The scientists behind this experiment argue that it's that sense of connectedness that causes all those positive benefits. And they cite something called the biophilia hypothesis as a possible mechanism for this. The hypothesis theorizes that since, evolutionarily speaking, we're used living in natural environments, we all have some innate urge to seek out nature.

The researchers suggest that we need to see ourselves as part of it, belonging to the same group as the various plant and wildlife species we share our planet with. It can be hard to prove evolutionary hypotheses like this, especially when they're as abstract as this one. But the concept that we need to belong to groups to stay mentally healthy is one of the main principles of social psychology research.

In fact, it's such an important concept that having a sense of belonging with other people is seen as a core human need in some models. Not having this sense of belonging can lead to things like lowered immune response, and poorer sleep quality. And, conveniently, those are exactly the kind of functions researchers have seen improve when we're exposed to natural environments.

So it's not that huge of a stretch to think that maybe that need to feel like we belong extends beyond human interactions, to seeing ourselves as part of the wider ecosystem on our planet. It's a plausible idea, and the results of this study certainly support it. But like with a lot of other big ideas, it would help to have more research to be sure.

If nothing else, though, studies do suggest that time in nature is really good for you. So even if we don't totally know why, it's probably worth visiting your local park sometime. Your brain — and your mood — will thank you.

Thanks for watching this episode of SciShow Psych! If you enjoy hanging out in nature and want to learn more about it, you can check out one of our new sister channels, Nature League! In it, SciShow Psych's very own Brit Garner explores all things wild — and takes you on some field trips as a bonus.

You can find it at youtube.com/natureleague. [ ♪ OUTRO ].