Honestly, I believe various things could push one to contemplate and ultimately commit, suicide.
As LevelThePlayingField pointed out, there is an incredible amount of pressure for each and every one to do more, every single convention isn't Love or Kindness, its about how YOU can improve your ministry or how YOU better stay obedient or else you will get shunned by your family while you're alive & then get killed at Armageddon (which is probably tomorrow so you'd better stick with US.)
I also think that, if someone IS shunned or disfellowshipped - the worst (and sadly, most likely) scenario is that they will be cut off from everyone that they've ever known, friends and family alike will treat them as if they have the plague or are dead and it is very hard once on the outside to actually know how to function on the outside and form bond.
Also - perhaps if one is disfellowshipped, and comes to the conclusion that God does not exist, and that there is no real meaning for us even being alive - that could be incredibly hard on someone, especially one whose been told their entire life that they were going to live forever on a paradise earth.