depression
"After taking Prozac successfully for about 10 years, I talked with my doctor about switching to a different anti-depressant because I missed having a sex-drive.  After a year on Citalopram, there was no change.  So I switched to Bupropion.  It caused me to feel very depressed and extremely anxious.  I am well aware that anti-depressants take several weeks to have positive effects and that the side effects also tend to go away.  So I stuck with the Bupropion for 6 weeks.  It just got worse and worse and I started to feel suicidal for the first time in my life.  I have been back on Prozac now for 2 weeks and am feeling a little better. Stopping Prozac just to try to get sex drive back was a big mistake."