[token78]

In my own experience, casual or minimal exercise has done little to affect my mood and since my early twenties depressive periods have been a very real problem, even effecting my employment at one point.

But going hard, and really pushing my body and pushing myself beyond my preconceived limits has done wonders. There have been times when getting that "runner's high" feeling has completely sidelined the depressive state I've been in. When it happens, I'm still astonished at how much that endorphin release can really make a difference to my mental well being. I realise this is all only anecdotal, with a sample size of one! But I believe runner's high is a recognised phenomenon:

http://en.wikipedia.org/wiki/Endorphin#Runner.27s_high