It doesn't increase aggression. If anything it moderates it. A depresed mind has a hard time maintaining focus. This is an obvious problem in the gym. The better you feel mentaly the better your body functions physicaly. By stablizing your mood it enables you to focus and not be distratcted by trivial things that once would bother you. It really does not hold that much benifit directly, but a psychologicaly sound mind is able to operate the body in a much better fashion.
5-10 grams of inositol + 100mgs of 5-HTP will do more for depression/anxiety than prozac or any other SSRI,and, unlike those drugs, these are natural products which do not cause sides and work immediately...
People tend to train with less intensity and miss more workouts on prozac, the reason being is that you feel good about yourself and the world around you, so why bother.