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Social isolation is a risk factor for depression, so arranging to go for a walk or a ski with other people lowers your risk.AlexBrylov/istock

If we learned anything from the Great Bicycle Shortage of last spring, it’s that now is the time to stock up on snowshoes, skis, boots, warm clothing and all the other gear you’ll need to get active and stay comfortable outdoors over the coming winter. Because let’s face it, your mental health may depend on it.

Even at the best of times, winter is challenging. About one in five Canadians report feeling “winter blues,” and a quarter of those experience more severe seasonal mood changes. Exercising and socializing are two good countermeasures, but it’s looking increasingly likely that we’ll have limited indoor options for both this year (and backyard beers will sound a lot less fun in February). That’s where the skiing – or snowshoeing, or hiking or whatever gets you moving outdoors – comes in.

Nearly 2,000 years ago, the physician Galen was already prescribing exercise for depression. But it’s only recently that researchers have reached a more definitive conclusion about its benefits. For mild to moderate depression and anxiety, “exercise is at least as effective as the two standard go-to treatments, therapy and medication,” says journalist Scott Douglas, whose 2018 book Running is My Therapy explored the links between exercise and mental health.

For winter exercise in particular, a study published last year in Psychiatry Research made a particularly compelling case for cross-country skiing. Researchers at Sweden’s Lund University and several other institutions examined the medical records of more than 197,000 people who participated in a famous race called the Vasaloppet, with distances ranging from 30 to 90 kilometres, between 1989 and 2010. They compared the skiers to an equal number of non-skiers, chosen to have similar age, sex and region of residency.

The unique nature of Sweden’s centralized medical records allowed them to exclude anyone previously diagnosed with serious disease or any form of mental illness. Then they checked the records to see how many people were diagnosed with depression in the years after they participated in the Vasaloppet, for up to 21 years afterwards.

The results were stark. The skiers, who presumably engaged in significant amounts of winter exercise to prepare for the race, were roughly half as likely as the non-skiers to develop depression.

In studies like this, there’s always a risk of reverse causation, since people with early and undiagnosed depression may be less likely to exercise in the first place. But when the researchers excluded anyone who was diagnosed with depression in the five years after they first participated in the race, the results were unchanged. That bolsters the causal claim that exercise reduces the risk of depression.

There are several theories about why exercise boosts mental health, such as reducing inflammation in the brain, boosting blood flow, or altering brain chemistry. But some of exercise’s indirect effects, like getting you outside and meeting up with friends, may be just as important, Douglas points out.

For example, there’s a large body of research suggesting that our brains respond favourably to being immersed in natural environments, which can improve mood and reduce stress.

“In addition to whatever might be going on with brain chemistry related to green exercise, I think there’s a practical aspect at play here, too,” Douglas says. “Skiing in the forest is more enjoyable than using a Nordic trainer in your basement.”

And if it’s more fun, you’re more likely to stick with the habit.

The same goes for meeting other people. Social isolation is a risk factor for depression, so arranging to go for a walk or a ski with other people lowers your risk. And, Douglas adds, it also makes you less likely to bail out if you know your friend is waiting for you.

One question that remains unanswered is exactly how much or how hard you need to exercise in order to reap the mental health benefits. The Vasaloppet study didn’t gather any information on its subjects' training habits, and other studies have reached mixed conclusions. The only truly consistent conclusion is that something is better than nothing – and, from a practical perspective, you’ll want to push hard enough to stay warm.

Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Twitter @sweatscience.

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