Vick, as I've stated before my Dr. had me try Prozac as a preventative for migraines. The 10 mgs (I think that was the dosage - it was the smallest you can get, whatever that is) didn't affect me at all so per his instructions, I doubled it.
I went into a clinical depression that even thinking back on it freaks me out. Of course, I knew what caused it and within 24 hours of stopping the medication I was fine, but I gained a VERY healthy respect for people who have clinical depression and can function in any way, shape or form. It truly was debilitating for me. Props to you for dealing with it and talking about it!