Exercise training and increased physical activity are effective for both prevention and treatment of depression, concludes a research review in the August issue of Current Sports Medicine Reports, the official journal of the American College of Sports Medicine. The journal is published in the Lippincott portfolio by Wolters Kluwer.

"The evidence of the use of physical activity and exercise for the management of depression is substantial and growing fast," comment Felipe Barretto Schuch, PhD, of Universidade Federal de Santa Maria, Brazil, and Brendon Stubbs, PhD, of King's College London, lead authors of the special "Exercise Is Medicine"' article. "Despite this substantial evidence, the incorporation of exercise as a key component in treatment is often inconstant and often given a low priority."

Studies support exercise for treatment and prevention of depression

Depression is a major health problem worldwide, with an enormous impact on mental and physical health for individuals and high costs for society. Current treatments focus on antidepressant mediations and psychotherapy, each of which can help people but have important limitations. For example, only about half of people taking antidepressants will have a clinically significant response, and not all people will respond to psychotherapy.

"[T]here is growing recognition that lifestyle behaviors, such as physical activity and exercise partially contribute to the risk of developing depression and can be useful strategies for treating depression, reducing depressive symptoms, improving quality of life, and improving health outcomes," according to the authors. They provide an updated overview of the growing evidence on the benefits of exercise for depression.

Across countries and cultures, studies consistently link higher levels of physical activity to lower depressive symptoms. But those cross-sectional studies don't answer a key question: Can starting an exercise program or increasing physical activity reduces the risk of developing depression or reduce depressive symptoms?

Drs. Schuch and Stubbs and colleagues analyzed pooled data on 49 prospective studies including nearly 267,000 participants. This meta-analysis found physical activity reduces the odds of developing depression by 17%, after adjustment for other factors. The protective effect was significant in all countries and across patient subgroups.

Physical activity is also an effective treatment for depression—some studies have shown that a single exercise session can reduce symptoms in patients with major depressive disorder. The authors performed another meta-analysis of 25 randomized trials in which nearly 1,500 people with depression were assigned to exercise training or comparison groups. The results suggested a "very large and significant antidepressant effect" of exercise.

But exercise may not be equally effective for all patients. A wide range of biological, clinical, psychological, and social factors affect the response to exercise therapy for depression, which may be helpful in matching "the right patient for the right treatment."

Research is ongoing to identify how the antidepressant response to exercise works. Potential mechanisms involving exercise-induced changes in inflammation, oxidative stress, and neuronal regeneration (particularly in the hippocampus) have been proposed. Yet, research investigating why and how exercise reduces symptoms is in its early stages, and the findings are not conclusive.

In any group of patients, starting and sustaining an exercise program can be challenging. Some reports have suggested that the key to successful exercise therapy for depression is "autonomous motivation": physical activity should be as enjoyable as possible, leading people to exercise for its own sake. Supervision by health and fitness professionals or social support from friends and family may also increase the chances of success.

Even though the evidence strongly supports the benefits of exercise, it still isn't routinely included in clinical recommendations for prevention and treatment of depression. The authors conclude, "Addressing this issue and the current reliance on the two-pronged approach of talking therapies and medication is important in going forward."