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Walking or gardening for as little as 20 minutes a day can help prevent depression, says a University of Toronto researcher who examined 26 years' worth of scholarly research.

Regular exercisers are well acquainted with that satisfying mood boost that comes after a brisk walk or bout at the gym. But the mental health benefits of exercise appear to last long after that runner’s high subsides, according to a systematic review published by Kinesiology and Physical Education PhD candidate George Mammen in the October issue of the American Journal of Preventive Medicine.

Mammen’s findings show regular physical activity may prevent the onset of depression later in life.

While a growing body of research supports that exercise can ward off stroke, heart disease and cancer, the mental health benefits of physical activity—especially in the long term, have not been as thoroughly explored. Increasingly, evidence supports that exercise is an effective treatment for existing depression, Mammen said, but less work has been done on prevention.

This is the first review to focus exclusively on the role that exercise plays in maintaining good mental health and preventing the onset of depression in the long term.

Supervised by Professor Guy Faulkner, who also coauthored the review, Mammen analyzed over 26 years’ worth of research findings from esteemed publications and renowned scholars to discover that even low levels of physical activity (walking and gardening for 20-30 minutes a day) can ward off depression in people of all age groups.

Mammen’s findings come at a time when mental health experts want to expand their approach beyond treating depression with costly prescription medication.

“We need a prevention strategy now more than ever,” he says. “Our health system is taxed. We need to shift focus and look for ways to fend off depression from the start.”

Mammen acknowledges that other factors influence a person’s likelihood of experiencing depression, including their genetic makeup. But he says that the scope of research he assessed demonstrates that regardless of individual predispositions, there’s a clear takeaway for everyone.

“It’s definitely worth taking note that if you’re currently active, you should sustain it. If you’re not physically active, you should initiate the habit. This review shows promising evidence that the impact of being active goes far beyond the physical.”

Valerie Iancovich is a writer with the Faculty of Kinesiology and Physical Education at the University of Toronto.