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THE QUESTION
I suffer from depression and my doctor has given me a prescription for antidepressant medication. She says my mood may improve if I also increase my level of physical activity. But I find it hard enough just getting out of bed in the morning – not to mention exercising. Can physical activity really help?
THE ANSWER
Numerous studies have found that people who regularly exercise are less likely to develop depression than those who have sedentary lifestyles.
Doctors who treat people with mood disorders have also noticed that exercise can help some of their patients feel better.
These observations certainly seem promising. But there is a dearth of large-scale studies that provide clear and definitive guidance on how exercise might be used to overcome depression.
What patients are most likely to benefit? What's the best type of exercise? What's the right amount? To answer these questions will require a substantial investment in more research, says Dr. Benjamin Goldstein, director of the Centre for Youth Bipolar Disorder at Sunnybrook Health Sciences Centre.
Of course, pharmaceutical companies spend billions bringing new drugs to market. But, unlike a patentable pill, there is not the same profit to be made from a prescription for exercise. As a result, the money devoted to exercise research lags far behind the dollars poured into drug development, Goldstein says.
Even so, a few things can be said with some certainty. Not every depressed patient improves with exercise. Similarly, not every patient gets better with antidepressants.
"We are beginning to recognize that depression is not just one disease – it may have several subgroups," says Dr. Madhukar Trivedi, a professor of psychiatry at the University of Texas Southwestern Medical Center in Dallas.
And, in particular, some depressed patients have elevated levels of Tumour Necrosis Factor alpha (TNFa) – which is a sign of inflammation occurring in the body.
Trivedi's research has found that patients with especially high amount of TNFa tend not to respond well to antidepressants, but many of them do feel better with exercise.
Although a lot more work is needed to explain this finding, it's possible that exercise counteracts the inflammatory process, which is somehow linked to depression.
"Exercise is like a biological sledgehammer that affects many different systems in the body, whereas medications are limited to a handful of mechanisms," Goldstein says.
It's also possible that exercise may boost the effectiveness of other treatments, including antidepressants and talk therapy.
Goldstein points out that patients with conditions associated with poor heart health – such as Type 2 diabetes and obesity – are also less likely to respond well to antidepressants. By improving their heart health through exercise, they may be indirectly improving their brain health by boosting their receptivity to antidepressants.
But there is a catch. Trivedi's research suggests that patients must exercise at a certain level of intensity to experience a meaningful reduction in their depression symptoms.
"This is not just a leisurely walk in the park," says Trivedi, who is considered a leading expert and has authored multiple studies on exercise as a treatment for depression. "It amounts to about 45 minutes of moderate-intensity exercise – where you're breathing heavily – three or four times a week.
If his calculations are correct, that amount of exercise may be a daunting challenge for certain patients who are in the grips of depression, which is often characterized by low energy levels.
Many depressed patients are further handicapped by a condition called anhedonia – in which they no longer derive pleasure from everyday activities including exercise. They may feel fatigued from a vigorous workout, but get none of the satisfaction from their accomplishment, Goldstein says. Anhedonia can undermine their motivation to keep exercising.
Goldstein suggests that patients adopt a gradualist approach to exercise, slowly building up the intensity of their workout. Some patients, he adds, may benefit from joining a gym or an organized exercise program that includes other people who may provide moral support and encouragement.
As part of his psychiatric practice, Goldstein often treats depressed adolescents who are the offspring of adults with bipolar disorder (manic depression). He hopes that someday there will be enough evidence to justify using exercise as part of a prevention package to delay the onset of depression or to avoid it entirely in people who are genetically predisposed to the condition.
"It's important to understand the biology that underlies depression so that we can better target treatments," he says. With hope, that knowledge will come with more research.
So, what are depressed patients supposed to do in the meantime? It's certainly worthwhile trying an exercise program under the guidance of your doctor. "After all, it's good for your heart and may also help your mood," Goldstein says.
Paul Taylor is a patient navigation advisor at Sunnybrook Health Sciences Centre. He is a former health editor of The Globe and Mail. You can find him on Twitter and online at Sunnybrook's Your Health Matters.