This post begins a weekly five part series exploring the mental health benefits of hiking, from a scientific and a first-hand perspective. The author has asked to remain anonymous, but if you stay tuned for all five articles, you will be amazed and inspired by the ending.

The Neurochemistry of exercise: why hikers seem so friendly

In my own experiences on long-distance hikes, the social aspect of my journey was especially therapeutic. People seemed friendlier. They seemed to care more. They were more considerate. They were more accessible. Conversations flowed more easily. I noticed that, normally a classic introvert, I began looking forward to meeting new people and spending hours with my new friends. Over time, I came to greet any hiker with a basic expectation that whatever interaction would follow would be positive. I’ve heard other hikers comment before on how “hikers” are “special” and tend to be “nicer than normal people.” It turns out this isn’t the whole story. This social phenomenon actually has to do with the neurochemistry of moderate-intensity exercise.

Exercise has long been known to boost endorphin levels, which increase pain tolerance and boost mood. A “runner’s high,” which arises from any moderate-intensity exercise lasting longer than 20 minutes, is traditionally associated with this endorphin spike. More recent research, however, points to the story of a different family of neurochemicals that become active during exercise: endocannabinoids.

“Don’t worry, be happy”

Endocannabinoids lock onto receptors in areas of your brain that regulate your stress response. When this happens, you experience a state of contentment. Anxiety melts away. For this reason, neuroscientists call endocannabinoids the “don’t worry, be happy” chemicals of the brain (1).  These chemicals also influence the brain’s reward system. This is why physically active people are significantly more optimistic than inactive people (2).

Endocannabinoid activity is induced only by moderately intense exercise. If you walk very slowly, you won’t experience a boost in endocannabinoids. If you sprint to the point of exhaustion, you’re also not going to see a boost in endocannabinoids. (3) Since hiking is almost always a moderate-intensity activity that lasts longer than 20 minutes, hiking is a sure-fire way to stimulate these powerful neurochemicals.

Endocannabinoids are also responsible for the social phenomenon we experience on trail. The release of endocannabinoids primes us to connect with others. Studies have demonstrated that exercise makes you more likely to share and cooperate with others. It increases the likelihood that you will have positive interactions with friends and family.(4) One study showed that after married couples exercise together, they feel more satisfied with their marriage and report more “positive marital events,” such as one spouse saying something to make the other feel loved, and listening to one another.(5)

So a hiking-induced endocannabinoid rush leaves you feeling content, relaxed, optimistic, and more connected to others – even more loved.

Exercise doesn’t only stimulate endocannabinoid activity. It also changes the structure of the system so that it functions more effectively. Exercise will increase the density of endocannabinoid receptors on your brain’s cells. This means that exercise makes the brain more sensitive to pleasure.(6) The benefits of a hike, then, are carried beyond the trail. Afterwards, any pleasurable activity will feel even better. You will enjoy meals more. A sunset will feel more awe-inspiring. You’ll feel more connected when you are around your friends. And the more consistently you hike or otherwise exercise, the more sensitive your brain becomes to these everyday pleasures.

This research has profound implications for mental health. Depression is the leading cause of disability in the US for ages 15 – 44 and affects 6.7% of the US adult population in any given year.(7) Anhedonia, or the inability to feel pleasure, is a common symptom of depression and other mental health disorders, including social anxiety, schizophrenia, and bipolar disorder (8). Because exercise sensitizes the brain to pleasure by way of the endocannabinoid system, it has the power to counteract the anhedonic effects of depression.

Another common feature of mental illness is social isolation. This is due in part to anhedonia because social interactions are no longer as pleasurable; and, especially for severe mental illnesses, due to the exhausting impact of social stigma. As a person isolates, however, they withdraw from one of the most powerful predictors of well-being and general health: social support. The role that moderate-intensity exercise plays in promoting social connection not only makes it a powerful antidepressant, but also supports a person’s very ability to recover from mental illness by encouraging the social connections that themselves are predictive of mental health in the first place.(9)

As will be discussed in upcoming articles, hiking provides further benefits – beyond the general benefits of exercise – to mental health and mental health recovery specifically because it takes place in natural settings.

References

(1, 3, 4, 6) McGonigal, Kelly. “Why does running give you a high? A look at the science.” ideas.ted.com. 28 April 2020. [https://ideas.ted.com/why-does-running-give-you-a-high-heres-the-science/]

(2) M Kavussanu & McAuley, Edward. “Exercise and Optimism: Are Highly Active Individuals More Optimistic?” Journal of Sport and Exercise Psychology. 1995. Issue/vol 17. 246-258.

(5) JB Yorgason, LN Johnson, MS Hill, & B Selland. “Marital Benefits of Daily Individual and Conjoint Exercise Among Older Couples.” Family Relations: Interdisciplinary Journal of Applied Family Science. 67(2). 227-239. doi: 10.1111/fare.12307.

(7) “Facts and Statistics”. Anxiety & Depression Association of America. 21 April 2021. [https://adaa.org/understanding-anxiety/facts-statistics]

(8) Brody, Barbara. “What is Anhedonia?” WebMD. 20 Oct 2020. [https://www.webmd.com/depression/what-is-anhedonia]

(9) TF Harandi, MM Taghinasab, & TD Nayeri. “The correlation of social support with mental health: A meta-analysis.” Electron Physician. 25 Sept 2017. 9(9): 5212-5222. doi: 10.19082/5212.