Depression  is a disease that afflicts millions of people and costs billions of dollars every year, and it is getting worse. One has to ask: besides the obesity epidemic, is our sedentary lifestyle contributing to a depression epidemic? Is exercise necessary for a healthy psyche? Can physical activity 'cure' depression?
In the last decade, a new kind of brain chemical has been discovered that plays a pivotal role in the healthy balance of the other chemicals in our brain. This chemical is called brain-derived neurotrophic factor (BDNF)  and is discussed by Rassmusen, et al. in the article 'Evidence for a release of brain-derived neurotrophic factor from the brain during exercise.' BDNF has been found to regulate the maintenance, growth and survival of neurons; to influence learning and memory; is low in patients with Alzheimer's Disease and clinical depression; and affects body weight, energy homeostasis, and blood glucose levels. In addition, genetic mutations of the BDNF gene are associated, in both mice and humans, with the entire laundry list of metabolic syndrome problems. Where does BDNF come from in our brain? Why does it affect so many aspects of a healthy self? What can we do to 'balance' our brain chemicals without resorting to Prozac® or Abilify®, which we are beginning to find out are more like temporary bandaids for a much deeper problem of brain chemical imbalance and are only slightly better than a placebo ?
Recent studies have shown that exercise raises circulating BDNF levels. Exercise has been found to enhance BDNF transcription  in the brain and to effectuate brain uptake  of insulin-like growth factor 1, which is a necessary ingredient for increasing mRNA expression of BDNF. BDNF has also been shown to promote  the health of serotonin-responsive neurons and to interact with serotonin-producing genes. Instead of a prescription for an antidepressant, should doctors be prescribing 30 minutes a day at the gym? And what if the exercise had the added benefit of reducing stress? What if doctors prescribed yoga classes instead of Prozac®? Could we expect to see even more benefits than exercise alone: reduced stress, improved mood, thinner waistlines, less Type II diabetes, and better sex lives? If I was depressed and yoga could do any of those things, it would be enough to undepress me, BDNF levels aside.
Recent studies show that there is a positive correlation between yoga and circulating BDNF levels. In his master's thesis , NL Pan discovered that a form of yoga called Sudarshan Kriya yoga (SKY) increased serum BDNF level in patients that had high initial depression indices, and as an added bonus, reduced cortisol. This effect was determined to be independent of circadian rhythm levels. Other researchers have investigated the effect of yoga on depression with positive results (Pilkington, et al. , Javnbakht, et al. , Janakiramaiah, et al. ) but linking yoga to BDNF levels is a more recent finding.
As controversial as the idea sounds, maybe it is time for doctors to stop doing the easy thing by prescribing a pill and just tell patients to get off the couch and go to yoga class. And if patients don't believe their own doctor, while they are sitting on the couch they can just tune into Dr. Oz, our new national guru of all things health, who promotes exercise as a cure for many ills. I don't mean to trivialize the problem of depression, but the idea that it is we ourselves who are responsible for our health, even our mental health, should not be revolutionary or controversial. But depression is like a lot of things these days: someone else or something else is supposed to provide an easy fix.