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We all know intuitively that being in nature makes us feel more peaceful. But why is this the case?

The Physiology of Depression

Your hypothalamus gland in the brain is responsible for the body’s homeostasis, or balance, with the outside world.  It regulates a number of functions, including body temperature, thirst (and thus, fluid balance and blood pressure), hunger, sleep, sex drive, bonding, “fight or flight” responses to threats, and mood.

The hypothalamus is one of several structures included in the brain’s limbic system, considered to be the seat of emotions in the brain.  Depression, whether organic or caused by an outside event, is associated with an overactive hypothalamus.

Neurotransmitters, or chemical messengers in the brain, associated with the hypothalamus are primarily serotonin (the feel-good neurotransmitter most often associated with treatment of depression in the form of SSRIs), and the catecholamines, a collection of neurotransmitters including dopamine, norepinephrine, and epinephrine. The latter two are also together referred to as adrenaline.

Depressive symptoms are typically associated with a deficiency in serotonin, catecholamines, or both.

Here’s how being out in nature can affect those levels.

Serotonin, Vitamin D, and Sunlight

The brain responds to sunlight by producing feel-good serotonin. Studies show that the brain produces more serotonin on sunny days than on overcast days.

But what we all probably know best about Vitamin D is that it, too, is produced in response to sunlight exposure. Plenty of studies show that low Vitamin D levels are also connected with depression, and when Vitamin D is given orally to depressed, deficient individuals, depression lifts. It turns out that Vitamin D also independently both boosts serotonin production, and blocks the breakdown of serotonin, much like SSRIs do. So sunlight is like a one-two punch: it produces more serotonin directly, and it also produces Vitamin D, which in turn makes more serotonin, and also prevents that serotonin from getting eliminated.

This may be part of the reason why Vitamin D receptors are present in the hypothalamus, the area of the brain primarily associated with depression.

Green Spaces

There is more to being out in nature than just sunlight, though. This study shows that connectedness to nature profoundly affects overall vitality and psychological well-being. Specifically, green spaces and abundance of birds are associated with decreased depression, anxiety, and stress. Green environments have also been shown to improve both self-esteem and mood, and even more so when the environment also includes water.

Even if you can’t actually get outside, bringing nature indoors can have a soothing effect. This study shows that surgical patients with plants and flowers in their recovery rooms have lower lower levels of pain, anxiety, and fatigue. Even listening to recorded sounds of nature can decrease anxiety and depression.

Nature has a way of giving us perspective on our lives that we might not have had otherwise. This study shows that natural environments caused participants’ focus to shift from “extrinsic aspirations”—those to do with earningdoinggoing, and acting—to “intrinsic aspirations”—that is, those to do with being.

Why does nature have these effects, aside from the direct and indirect neurotransmitter alterations from sunlight? We still don’t know for sure, though I wonder if it might have to do with the fundamental Schumann resonance, or the frequency of the earth’s vibration. While the Schumann resonance fluctuates based on the density of earth’s ionosphere, it fundamentally hovers around 7.83 Hz—very similar to the frequency of alpha brain waves, which are between 8-12 Hz. Alpha waves are associated with calm focus, relaxation, and reduced depression. Being out in nature may thus act to“tune” our brains to a calmer frequency: the frequency of the earth itself.

Green Exercise

Exercise alone is considered to be a powerful natural antidepressant for mild to moderate depression, probably because it raises catecholamines as well as endorphins.

Combining exercise with being in nature (“green exercise”) is even more effective than either one alone. Green exercise can include hiking, biking, walking, jogging, kayaking, canoeing, and a myriad of other outdoor activities. Exercising in a gym is good, but getting out into nature is better!

The Upshot

If you’re struggling with anxiety or depression, getting out into nature, and especially engaging in outdoor activities, is a great way to raise Vitamin D and improve neurotransmitter balance. Nature also encourages calming, mood-lifting alpha brain waves. Combining a green environment with the feel-good catecholamines and endorphins of exercise is a great way to hit a mental “reset button.”