Exercise to relieve depression

There is an unorthodox treatment for anxiety and mood disorders, including depression. It is free and has no side effects. Meanwhile antidepressant drugs cost Americans $10 billion a year and have many common side effects: tremors, sleep disturbances, nausea, changes in body weight.

The treatment is exercise. I think many already know this without conducting a study. For many people exercise results in them being in a better mental state.

Highlights from this time magazine article, Is Exercise the Best Drug for Depression?

• Observational studies showed that Americans who exercised were not only
  less likely to be depressed than those who did not, but were also less likely
  become depressed in the future.
  
• In 1999, Duke University researchers demonstrated in a randomized controlled
  trial that depressed adults who participated in an aerobic exercise plan
  improved as much as those treated with sertraline, the drug that was marketed as
  Zoloft, and was earning Pfizer more than $3 billion annually before its patent
  expired in 2006.
  

Subsequent trials have repeated these results, showing that patients who undergo aerobic exercise regimens see comparable improvement in their depression as those treated with medication. Exercise boosts mood. It not only relieves depressive symptoms, but appears to prevent them from recurring.

At this point, the data on exercise are only suggestive. The article goes on to state that the trials have been small and most have run only for a few weeks and that the trials have by methodological problems. Still, despite limited data, the trials all seem to point in the same direction:

They speculate that exercise primes the brain to show less stress in response to new stimuli.

“A little bit of mental strain and excess stimulation from exercise, in other words, may help us to keep day-to-day problems in perspective.”

“A little bit of mental strain and excess stimulation from exercise, in other words, may help us to keep day-to-day problems in perspective.”

Researchers also wonder whether this interaction between body and brain may, evolutionarily speaking, be hard-wired. "It occurs to us that exercise is the more normal or natural condition, and that being sedentary is really the abnormal situation.".