depression
"Worst experience I've ever had on any medication.  My doctor started me on a small dose.  Within 30 minutes of taking it, I felt a buzzing in my head and a fuzzy, numb feeling.  Then, about an hour later, the really bad side effects kicked in.  My heart started racing and feeling like it was going to explode.  I started hearing voices.  I felt so bad I almost called 911 -- I couldn't even stand up or lay down -- just laid propped up on the couch for about 24 hours until the effects started wearing off.  It was the scariest experience I've ever had and made me afraid to take any other anti-depressant."