Those who aren't depressed sometimes wonder why those who are won't just snap out of it. However, depression is a serious illness that comes in many forms and is caused by a combination of genetic, environmental, biological and psychological factors.
Now there is evidence to show that you may be able to sweat your way out of depression — though, admittedly, research on the effect that regular exercise has on the brain isn't nearly as conclusive as that proving the myriad physical health benefits for the body.
"There are relatively few studies that have been done right," said Tim Church, a professor of preventive medicine at the Pennington Biomedical Research Center in Louisiana. It's a difficult area to study because, Church explained, seriously depressed people don't want to show up for an exercise study.
And other factors can skew the results, he added. "Depressed people are going to benefit just from interacting with the people running the study," he said. "The exercise staff can become the only stable relationship in this person's life."
So the question can arise: Was it the workout that alleviated depressive symptoms or the personal relationship with the staff?
Despite these concerns, exercise does have a track record of positively affecting the brain — it has been proved to decrease stress, reduce risk of dementia and enhance cognitive function for dealing with food.
But can it also be used as a tool to combat depression?
Church is adamant that it can. He spoke of a carefully controlled study conducted by exercise science researcher Andrea Dunn that limited the interaction between staff and patient to focus on exercise as the sole intervention for depression.
"The people in the study were clinically depressed," Church said. "(The group) in the low-exercise intervention experienced 20 percent complete clinical remission, and the high-exercise group was 40 percent clinical remission. The higher exercise results are right in line with (results from an) anti-depressant medication like an SSRI (selective serotonin reuptake inhibitor)."
The "high" exercise dose in this study, published in 2005 in the American Journal of Preventive Medicine, was referred to as the "public health dose" because it was in line with public health recommendations for physical activity. The study concluded that "aerobic exercise at a dose consistent with public health recommendations is an effective treatment for (major depressive disorder) of mild to moderate severity. A lower dose is comparable to placebo effect."
The higher, public health dose equals burning 8 calories per pound of body weight per week. So, if you weigh 200 pounds, that's 1,600 calories worth of exercise a week. (In Dunn's study, the low-exercise intervention burned 40 percent of the calories burned by those in the high-dose group.) Some consider the high-exercise prescription a lot, but it's far from unreasonable. Working out at moderate intensity, it translates to roughly four hours of exercise per week. Go hard, and it can be done in as few as two hours. But, as with medication, the assumption is that patients have to stay on the exercise regimen to stay in remission. It's a treatment, not a cure.
Dr. Antonia Baum, a psychiatrist in Chevy Chase, Md., who is on the faculty at George Washington University, sometimes prescribes exercise for depressed patients instead of pills.
"I take a sports history on my patients to find out what role being active has had on their lives and how important it has been to them," Baum said. "I try very hard to get them to incorporate exercise into their treatments for mood disorders or depression."
But she stops short of calling it a panacea.
"Attitude is important," Baum said. "Sometimes it's hard for people to get started with exercise. Part of the diagnosis of depression is lack of motivation and low energy, and this can make it quite difficult."
To motivate depressed patients to exercise, Baum said, "I approach it with a sense of humor but also remind them of how much fun and how exhilarating it can be." She likes to bring her bike into her office as a strategically placed prop.
Baum also gives them specific instructions about getting up and being physically active, sort of a "take four times per week in the morning with food" approach.
She added that her depressed patients who comply with her exercise prescriptions always do better than the ones who don't, but she admits that this may simply reflect their ability to rise above the depression and get active.
"It can partially be attributed to being the type of person who can persevere with exercise," she said. "They can also persevere at overcoming depressive symptoms."