My other thought was that, if you are depressed and/or suicidal, you are most likely thinking about death, and being dead. If you are thinking about those things, it just may happen to you, you might get yourself killed because of it; thinking sub-conciously about it. Kinda like when you have a negative thought process ALL the time of the day ahead, well... it will be a negative day, if you think and believe it will happen...