Exercise offers some benefits for people suffering from depression, according to an updated systematic review published in The Cochrane Library. However, researchers agree further studies need to be done in order to reach a more conclusive statement regarding the link between the two.

Researchers pooled the results of 39 smaller studies into exercise and depression and found that exercise did have a moderate effect on depression symptoms compared with having no treatment at all. However, when researchers looked closely at the studies, which included 2,326 people diagnosed with depression, they decided that most of them weren't conducted well enough to be very reliable.

In 35 trials comparing exercise with control treatments or no treatment, the researchers saw moderate benefits of exercise for treating depression. Exercise was as effective as psychological therapy or taking antidepressants, although these findings were based on only a few, small, low quality trials.

"Our review suggested that exercise might have a moderate effect on depression," said one of the authors of the review, Gillian Mead of the Centre for Clinical Brain Sciences at the University of Edinburgh in Edinburgh, UK. "We can't tell from currently available evidence which kinds of exercise regimes are most effective or whether the benefits continue after a patient stops their exercise program."

"The evidence about whether exercise for depression improves quality of life is inconclusive," the authors write. "Further larger trials are needed to find out whether exercise is as effective as antidepressants or psychological treatments."

Statistics show that more than 120 million people suffer from this mental disorder. Depression is most often treated with antidepressants, psychological therapy, or a combination of the two. Drug therapy can cause side effects that some patients find unacceptable, adherence can be a problem, and the drugs often require several weeks to produce a noticeable effect on symptoms, the authors noted in the background to their analysis.