Exercise lowers risk of depression at all ages, researchers find

Exercise helps protect against depression regardless of age or location in the world, a large new analysis suggests.

Researchers pooled data from 49 studies to create a sample of more than 266,000 people on four continents to examine the role of physical activity in preventing depression.

"The key message is that really when it comes to exercise and our mental health that something is better than nothing," saidstudy author SimonRosenbaum, senior research fellow in the School of Psychiatry at the University of New South Wales in Australia.

"And if you're doing something, try to add a little bit more."

The findings were published in Tuesday's issue of the American Journal of Psychiatry.

Rosenbaum said the meta-analysis builds on a growing body of evidence on how exercise can also be an important part of treatment for people living with mental illness.

Those who followed weekly guidelines to get 150 minutes of moderate aerobic activity, such as cycling or brisk walking, were less likely to develop depression over nearly eight years of followup compared with those who didn't meet the guideline.

The challenge is to support people to take the first step to get active, said Rosenbaum, an exercise physiologistwho also works at the Black Dog Institute in Sydney, a non-profit mental-health facility.

Offering enough social support, access and the right environment canhelp, he said.

'A more static human population'

Rosenbaum, who kayaksand does rock climbing, suggested that peopledo physical activity they enjoy and that they can fit into their routines. That way, they're more likely to keep it up in the long term.

The Canadian mood and anxiety treatment guidelines for mild to moderate depression say there's good evidence of exercise as a treatment, said Dr. David Goldbloom, a psychiatrist and senior medical adviser at the Centre for Addiction and Mental Health in Toronto. He was not involved in the research.

"We live in an age where between limitless streaming of TV, the paralytic effect of social media on human movement and the erosion of physical education [we are] creating a more static human population," said Goldbloom.

"Particularly when it comes to physical activity in high schools, this is the population that's really at high risk of developing their first episode of depression, so inculcating exercise into the culture of adolescence to a greater extent could have important mental health spinoffs."

One size does not fit all

Goldbloom said a more detailed Norweigan study published last year that followed people in that country for 11 years suggested as little as one hour of exercise a week could lower the risk of depression by 12 per cent.

Given the costs of depression to individuals, their families and to society, that's a substantial finding for a relatively benign intervention of exercise that should be in everyone's grasp, Goldbloom said.

"This is not a Speedy Muffler guarantee against depression, rather it's a way of lowering the risk of depression."

For instance, athletes aren't immune from the mental illness.

Exercise isn't the only answer and no one size fits all, Goldbloom said. A combination of exercise, antidepressants and psychotherapy often works best.

The studies in the review did not objectively measure physical activity, so some may have overreported how much they did. No one knows how exercise actually lowers the risk of depression.