depression
"When I was put on Prozac at the hospital, they prescribed 10mg.  At this dosage, I would have what I can only describe as "dips" in my mood.  It was like I had become become bipolar without "highs".  I would go from happy or sexually aroused one minute to wanting to cry the next.

So I went to my psychiatrist and explained that to her, so she increased my dosage to 20mg (which I think is the norm anyway).  Since then, I have been doing much better.  I'm actually a functional and productive human being again. I can thank Prozac for preserving my sanity."