Suicide is an escape mechanism. If viewed in that way, then it is not inherent proof of mental illness.
You’re Bernie Madoff in alternative dimension. You’ve been caught. Instead of going to prison, you put a gun to your head. Completely rational as a way of escaping punishment.
You’ve been kidnapped by foreign invaders and forced into the cramped quarters of a ship’s hull along with hundreds of other people. You have no idea where you are going, but you know it can’t be good based on the hell you’re already enduring. So you decide to leap off the side of the ship the first chance you get. Completely rational as a way of escaping pain and terror. Neither brave or cowardly…it’s a choice that defies judgment.
We’ve already covered health problems, both of the body and the mind. For the latter, I’m thinking of the torture of hearing loud, scary voices constantly. You kill yourself to get away from that, just as someone would kill themselves because of excruciating chronic physical pain. The proximate cause is a mental illness, but it’s not like the voices commanded you to commit suicide. You killed yourself to escape the pain that happens to dwell in your mind. Completely rational, though hard for some people to understand.
You accidently do something tragic, like driving a little too fast on black ice and mowing into a schoolyard full of kids. Or you leave something burning on the stove and accidently kill your whole family. The guilt is too much to bear and no amount of comforting from others can console you. You commit suicide because you feel like you don’t deserve to live anymore. I would say this is not rational, though the reaction is completely understandable. It is not a rational thought to believe that you don’t deserve to live because of something you did on accident. On purpose, maybe, but on accident? And everyone knows it and feels bad for you? But even though the thought itself is not rational, is this mental illness? I’m really not sure. A person can believe all kinds of irrational things (like that a supreme being is constantly watching them, despite the lack of empirical evidence) and still be mentally well.
Is it always irrational to hate one’s self? What if a person wakes up one day with tremenduous guilt for all the real horrible things they’ve done to others. Perhaps their meanness was motivated by a mental disorder or substance abuse, but the guilt or self-hatred would be an understandable reaction whatever the cause. So I could see someone committing suicide not due to a mental illness but because they finally have awareness of how they have negatively impacted people. They would be escaping the pain created by this realization. That would make it rational. So I guess this person is really no different than the accidental killer.
So the more I think about it, no, suicide is not inherent of mental illness. It is proof of pain, though. There may be a very tiny number of people who have committed suicide just for kicks, but I think pain is the underlying theme for all suicides. I guess it doesn’t make sense trying to categorize that pain. Though I still think survivors are free to feel whatever they want. If I commit suicide, I certainly wouldn’t expect everyone to understand or feel sympathy. And as I wouldn’t want to be judged for the feelings that drove me to my action, I don’t think it would be fair to judge others for theirs. Feelings can’t be helped.