Because, lets face it, depression isn't the only psychiatric illness out there. Antipsychotic medications are known to have a pretty hardcore weight gain side effect. How about all the other people out here who are on things other than ssris/ssnris????
For me, Thorazine and Haldol are the real butt kickers, they are SO HELPFUL, but the weight gain makes them pretty much not worth it
Edit: take that back, risperidal was the WORST. A high dose of that coupled with an involuntary stay on a psych unit with no smoking: 40 pounds gained in a month. Awful!!!!!!!!