depression
"I started Wellbutrin after taking Zoloft for several years.  The Zoloft was not effective anymore, though it had worked perfectly for a long time.  Wellbutrin nearly killed me.  I was more upset, anxious, and suicidal than I had been in years.  For some reason, it just did not agree with me chemically.  Afterward I went on Remeron.  That was an experience to read about!"