I'd really like to see the studies you're referring to, if you have any sort of identifying information I could use to find stuff about not repeating the study about benefits of exercise in depression. Because I work in an medical environment and "exercise works as well as meds" is pretty much the received wisdom, albeit with the caveat that "as well as meds" is actually not very well at all, only a small proportion of people with depression get real long-term improvement with anti-depressant medications alone. What I'd heard is that exercise, talk therapy, conventional anti-depressants, and some herbal medicines notably St John's Wort, are about equally effective, which is to say not very but they do help (different) small proportions of people. But that to get real long-term improvement you need a combination of most of those.