Is suicide a sin if the person is not mentally competent to be responsible?
It is well accepted today that the cause of the majority of suicides is mental illness. Yet in most of Judaism, Christianity and Islam suicide is considered self-murder in many if not most cases.
The Bible does not specifically address suicide as the sin of self-murder, but nonetheless it is widely forbidden.
Even though Islam condemns suicide in the scriptures, many justify suicide bombing as martyrdom.
The Baha'i Faith condemns suicide, and considers suicide a tragedy, but allows considerable leeway on the circumstances of the suicide, and allows for the contemporary behavioral science understanding of suicide as a mental illness.
This more a discussion of the different views and changing views in churches and other beliefs facing the issue in the contemporary world. The problem is the tragic rise of suicides throughout most cultures of the world.
I suppose it could also depend on how one defines suicide. What about reckless behavior, such as driving too fast or some other dangerous, risky activity which could lead to death? Or unhealthy activities, such as cigarette smoking, drug use, alcohol? They may not cause immediate or certain death, but they could be contributory factors in one's early demise.
As for intentional suicide, I would also wonder if religion (or God, if one exists) would consider other individuals responsible for an individual's suicide. For example, if a man commits suicide because his wife left him, would the wife also be considered spiritually/morally responsible? Are parents spiritually/morally responsible for the suicide of their child?