This is a well-known problem when treating severely depressed people with anti-depressants.
It makes sense, though. I had a very depressive roommate years ago, and it seemed like the defining characteristic of her depression was sometimes having an insurmountably high activation energy for seemingly mundane tasks, and being painfully conscious of it. Somebody who was full of frustration / anger from fighting that all the time, but suddenly able to follow through could really take it out on themselves. (She eventually transcended her problems, and was still a cool to know in her worst moments.)
That's a really good description.
However searching quickly, http://www.washingtonpost.com/wp-dyn/content/article/2006/12... verifies the link between anti-depressants and suicide. And further verifies that the link is short-term, but long-term they help.