Are anti-depressants over prescribed? Sure. Are there cases where the root cause of depression is biochemical? Yes.

I've been on meds for bipolar for five years, and I see a therapist every week. The meds get me stable - like healing a broken broken leg - and the therapy is my personal trainer building me up to run the marathon. Neither would be as effective without the other, but in my case, if I could only have one, it'd be the meds.