bipolar disorde
"Possibly the worst mental med I've ever taken, & I've taken many over the years.  It gave me an intense derealization side effect (only time I've experienced this, & it was unsettling as hell), and truly horrible, constant gas (as in, so bad I couldn't be in public)!  
Those who were brave enough to hold their breath & be around me told me that my affect was pretty flat as well.  So basically it made me freaked out, flat, & repulsive all at the same time: thumbs down."