*I got tired of hearing about how exercise reduces symptoms of depression and that the incidence of depression among regular exercisers, so when an opportunity to look at the reverse appeared, I took it. Here is a summary of my research (“lit review”/”background review” for you nit pickers).*

Exercise normalizes the body’s functions. For example, if a person with high blood pressure were to continue on a long-term exercise plan, blood pressure would be reduced. Exercise works the other way, too; a person with very low blood pressure who follows a long-term exercise plan will find their blood pressure rising into the body’s optimum range. Likewise it reduces the effects of insulin resistance (in other words, it increases the body’s sensitivity to existing insulin levels), which is why exercise is often part of the management plan for diabetics.

Exercise has a similar effect on the brain, and therefore, mood. In a normal person, exercise releases endorphins, increases serotonin and norepinephrine levels, and reduce cortisol levels, all of which result in an increase in perceived mood. Unfortunately, such is not always the case with those who suffer from depression. There is a high correlation between patients with major depressive disorder and those with smaller than average hippocampal regions with less neurogenic activity in the region affecting both memory and mood. (Lorenzetti, Allen, Fornito, & Yucel, 2009)

What exercise will do for the depressed client is: reduce cortisol levels and increase endorphins. There are conflicting studies as to whether or not levels of neurotransmitters are changed via exercise; however a recent study involving mice demonstrates that exercise decreases observable depression-type behavior even when tryptophan levels (a precursor and limiting factor for serotonin) were kept low. This indicates that, as with diabetics, exercise may increase the brain’s sensitivity to existing levels of neurotransmitters rather than affecting the concentration of neurotransmitters. (Lee, Ohno, Ohta, & Mikami, 2013) Other studies have shown that there is a lower rate of incidence of depression in regular exercisers. (Strawbridge, Deleger, Roberts, & Kaplan, 2002)

There is a vast pool of literature that tests and retests these conclusions. Few doubt the benefits of exercise on depression. Unfortunately this picture is incomplete. Those who are chronically depressed tend to find it irritating when these and other studies are quoted and we are expected to be motivated. Among other things, we’ve been assured that everything from St. John’s Wort to Prozak will make things better. When treatment after treatment fails, it’s hard to have faith in yet another lifestyle change. The Missing Piece

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