Does anyone here exercise on a regular basis? Do you notice how well it works for you, if at all, for reducing symptoms?

I have major depressive, PTSD, and anxiety and panic disorder. Due to my trauma, I also suffered physical disruptions as well. Because of, at first, the physical and now the mental added on, I was not able to do any kind of exercise or anything. At one point I couldn't walk at an average pace for a couple of minutes without my back hurting intensely. I'm at a better point…

Does exercise really make that much of a difference?