Arguably, one of the most interesting physiologic effects of yoga is at the hormonal level. Yoga, as is true of many other forms of exercise, increases levels of serotonin, dopamine, oxytocin and endorphins and decreases circulating cortisol and monoamine oxidase. Increased endorphins, of course, are felt to be responsible for the runner’s high. Alterations in oxytocin levels may be involved in mood disorders. Effects of serotonin, dopamine and monoamine oxidase levels on psychiatric illnesses have all been extensively studied. Monoamine oxidase inhibitors (MAOI), such as Nardil and Parnate, have been used in the treatment of depression since the 1950’s. Medications such as Wellbutrin boost brain dopamine levels. Selective serotonin reuptake inhibitors (SSRI) are the most widely prescribed antidepressants. SSRIs, such as Zoloft, Prozac and Paxil, block the reuptake of serotonin by cells in the brain, thereby increasing the amount of available serotonin. Quite simply, serotonin, dopamine, oxytocin and endorphins are the so-called “happy hormones”. The mechanism for the release of these hormones is certain to be complex and multi-factorial. Whether it be the activation of mechanoreceptors in fascia and muscle that initiate hormonal release, factors relating to changes in autonomic balance or conscious perceptions and expectations of peace and contentment, the practice of yoga gives us a literal boost as it causes the influx of happy hormones into the neural synapses of the brain. In this regard, might yoga be considered a natural antidepressant?