One in five Canadians will suffer from a mental illness in their lifetime, costing the Canadian health care system over $7 billion a year. While medications and counselling can help, Canadian researchers are looking at what could be one of the simplest and cheapest ways of preventing mental illnesses: exercise.

Judy Chu,a kinesiologist who runs fitness classes for seniors at the Baycrest retirement home in Toronto, knows that fitness can lift the mood.

“I see it working all the time,” she tells CTV News. “It’s like an antidepressant. But without taking medication, they are taking exercise.”

Baycrest residents say they like it, too.

“It does a lot. It improves my mind and my body and everything,” says 90-year-old Carmen Tayar.

“It works off all the stress and tension,” adds 88-year-old Leonard Parks, who exercises three times a week.

Canadian research is backing that up.

Rachael Stone, a researcher and PhD candidate who’s exploring aging and chronic disease at York University, recently completed a study on the effect of exercise in those over the age of 50.

Focusing on 44,000 participants in the 2007-08 Canadian Community Health Survey, she found that those who exercised 30 minutes a day had a 15 per cent lower risk of developing a mental illness that those who were mostly sedentary.

Those who exercised in group classes had a 45 per cent lower chance of developing a mood disorder. And those active in both group and individual environments were 59 per cent less likely to have a mood disorder than those who were not participating in either.

“I found that definitely, exercise has a protective effect against the prevalence of developing common disorders like depression and bipolar,” Stone says.

Stone says previous research has shown that seniors who take part in group exercise tend to have higher attendance rates and stick with an exercise program longer compared to those who commit to exercising alone.

Research has also shown, she says, that the psychological benefits from exercise can be comparable to the benefits from psychotherapy.

With all the known benefits of exercise, scientists at the University of Saskatchewan wanted to know what would happen if more Canadians got away from the couch and the computer desk and exercised more.

They estimate that if just 10 per cent more Canadians exercised 30 minutes a day, there would be 167,000 fewer diagnosed of depression and anxiety. A 25-per-cent increase in the numbers physically active each day would translate to an astounding 389,000 fewer cases of mental illness.

“Modest levels of physical activity have big payback. The evidence suggests that physical activity is as effective as antidepressants treatment,” Carl D’Arcy, a researcher at the University of Saskatchewan who specializes in the prevention of common psychiatric, mood and anxiety disorders.

“If we increased levels of physical activity we could substantially reduce the amount of mental disorders in the population,” he says.

And, he points out, it’s low-cost and accessible.

“What more can we ask for? It's not going to break the bank and it might even save us money,” he says.

D’Arcy says that physical activity is so effective as an antidepressant for those with mild to moderate depression, doctors should “prescribe” it at the same time as other treatments.

“It’s not an either-or situation, but a supplementary situation.”

Exercise offers benefits in a myriad of ways: it improves blood flow to the brain; it helps release “feel-good chemicals in our brains” while distracting us from negative thoughts; it promotes more social engagement and networking.

And then there are all the ways exercise can improve physical health, such as improving sleep, facilitating weight loss and leading to a better sex life  – all of which can improve mood just on their own.

Researchers say it’s not important how precisely exercise lightens moods; the important thing is to just start moving.

“Any kind of activity is better than no activity,” says Stone. “Even walking for 30 minutes will have an effect.”

With a report from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip