For most people, the benefits of exercise to their physical health was evident the very first time they stepped into gym class as a youngster. Exerting oneself through physical activity has always been instantly associated with physically healthy behavior. However, an increasing amount of studies have suggested the numerous benefits of exercise also extend to one’s mental health, especially for those suffering from depression.
According to the National Institute of Health (NIH), each year, depression costs at least $30 billion in lost productivity. The leading cause of disability in the United States, depression affects nearly 10 percent of the U.S. population, or roughly 19 million Americans. While treatments for depression have differed greatly over the years, regular exercise has traditionally shown positive effects for those suffering from depression. A 1991 study titled, “The Effect of Exercise on the Moderately Depressed Elderly,” divided groups of depressed men and women into three groups: an exercise intervention group, a social support group and a wait-list control group. Despite the exercise consisting of just a 20- to 40-minute walk three times a week for six weeks, the exercise group was better able to alleviate physical symptoms of depression than the other two groups.
Numerous other studies have taken place and shown the value of exercise as well. Results have repeatedly shown that the type of exercise or its frequency or duration is largely inconsequential. A 1998 study by Dr. Lynette L. Craft, Ph.D., titled, “The Effect of Exercise on Clinical Depression and Depression Resulting from Mental Illness: A Meta-Analysis,” showed that only the length of an exercise program proved to be a greater moderator, with programs nine weeks or longer showing greater reductions in depression. The same study also showed that age, gender or severity of depression did not act as moderators, meaning exercise as a means to combatting depression is beneficial to sufferers regardless of who they are.
Another interesting note came in a 2001 study coauthored by Dr. Debbie A. Lawlor and Dr. Stephen W. Hopker. Titled, “The Effectiveness of Exercise As An Intervention in the Management of Depression,” the study showed that fitness gains were not even necessary for patients to experience positive benefits. Such a revelation is of great value, as sufferers from depression who are not physically fit and might be averse to exercise can rest assured that the relief of their depression is not correlated with how many pounds they lose.
With so many studies now showing exercise as a viable option for relieving the symptoms of depression, many in the scientific community have offered their hypotheses as to why this is so. While these are just theories, they do offer interesting insight into why exercise can be such a great aide to those suffering from depression.
This hypothesis suggests that a rise in core temperature following exercise is responsible for the reduction in symptoms of depression. This implies that a feeling of relaxation and a reduction in muscular tension are a result of increases in temperature in certain regions of the brain after exercise. Though this hypothesis has been proposed, the research to support it has only examined the relationship of exercise on feelings of anxiety.
Another physiological approach, this hypothesis is rooted in the belief that exercise relieves depression thanks to an increased release of B-endorphins, which have a pain-relieving effect akin to that of morphine. Debate remains, however, as to whether these endorphins (there are many types) are reflective of endorphin activity in the brain. But numerous studies have shown a substantial increase in B-endorphins after exercise.
Arguably the most promising of the physiological hypotheses, the mono-amine hypothesis states that the exercise increases the availability of brain neurotransmitters that are diminished when a person is suffering from depression. These neurotransmitters, such as serotonin and dopamine, are known to increase in a person’s plasma and urine after exercise, but it remains uncertain if they increase in the brain as well.