N=1, but exercise was not useful for me. If anything, the cool-down period afterwards just encouraged me to avoid doing anything, and the pain of strenuous exrrcise also added to the misery index.

I did, however, find a medicine that worked wonders. Since then, I have worked out 30-45 minutes 5 days a week, but I certainly don't notice a difference in mood from before and after i started working out again.

Edit: I want to make clear that this is not a rebuttal of what worked for you, but a point to consider when discussing with others who may be suffering. If you speak in absolutes about what works, and they find that it does not work for them, they may end up feeling even more hopeless.