Suicide is wrong but let God be the Judge.

Suicide consists in the voluntary and intentional taking of one's own life, particularly where the person involved is accountable and has a sound mind. Mortal life is a gift of God; it comes according to the divine will, is appointed to endure for such time as Deity decrees, and is designed to serve as the chief testing period of man's eternal existence. It is the probationary state or time during which man is tried and tested physically, spiritually, and mentally. No man has the right to run away from these tests, no matter how severe they may be, by taking his own life. Obviously persons subject to great stresses may lose control of themselves and become mentally clouded to the point that they are no longer accountable for their acts. Such are not to be condemned for taking their own lives. It should also be remembered that judgment is the Lord's; he knows the thoughts, intents, and abilities of men; and he in his infinite wisdom will make all things right in due course.
-Bruce R. McConkie, Mormon Doctrine, p. 771, Suicides Copyright by Bookcraft


The General Handbook of Instructions (1989) says, "A person who takes his own life may not be responsible for his acts. Only God can judge such a matter. A person who has considered suicide seriously or has attempted suicide should be counseled by his bishop and may be encouraged to seek professional help" (11-5).
as quoted in Encyclopedia of Mormonism, Vol. 3, Suicide Copyright © 1992 by Macmillan Publishing Company