Re: Exercise Decreases Depression --> Why?
This is a little out there but... In another thread in this forum I have posted a journal article which outlines the relationship between physical fitness and mortality. Perhaps there is an innate, inherent drive within the human individual toward as long a life asa possible and this is driven by a mechanism which associates (or even rewards) activites which can prolong the life cycle (such as exercise, good nutrition, sunshine etc) with feeling good (general well being, good mood etc.). Similarly, activities of detriment to the life cycle (inactivity, poor nutrition, insufficient sleep, lack of sunshine) are discouraged by stimulating feelings of depression.
Also, if you are interested in the area of depression, suicide etc it is interesting to investigate the association between weather and suicide rates. The very high levels of suicide in Ireland (compared with mainland europe) are often associated with the dull, rainy climate here. I think studies have been done on this topic but do not know of any off hand.