How does thought of suicide enters a human mind?

It has puzzled biologists how such apparently detrimental behavior can ever evolve. Since anyone who commits suicide would be less fit, either because he/she will fail to reproduce or he/she will not be able to provide needed parental care to their offsprings. Besides, such a gene would almost certainly disappear from the gene pool if it ever evolves in an individual since he/she may die before passing on the gene. The short answer is that there is no gene that codes for suicide, so we don't need those fancy inclusive fitness/sociobiological arguments that were so fashionable in the 1980's. We don't need sociobiological arguments that claim that such a gene may in some perverted way be beneficial to the relatives of the suicidal indivduals and these relatives would then pass on the gene since they are likely to have it too. To me those sociobiological arguments are just plain BS.

Animals are shaped by evolution to escape from stress, because stress is not good for them physiologically and because stress often means danger. In other words, our instincts drive us to do things that will prompt us to get rid of stress. When stress becomes too much for an individual to handle, then they may contemplate ending his/her own life to find relief from the stress. Some people deal with stress differently, by trying to numb their pain with alcohol or pain killers for example. That is why many people can often be talked out of committing suicide and why suicidal behavior can persist. The gene that allow animals to escape stress is obviously beneficial, as is the gene that make us seek out sugary tasting food. Just as sugar can cause health problems for modern humans, the need to find relief from stress can sometimes result in tragedy. It is an unfortunate manifestation of what is normally a beneficial instinct.

Many people have suicidal thoughts at some time during their lives. For most the thought is fleeting, happening after a major life loss, or at some point in life where they perceive the future as becoming hopeless. For others, life is not quite so kind, they may have a strong genetic propensity to become depressed, a chemical imbalance, or a series of unfortunate life experiences may eventually end in depression. Still others have much to do with causing their own pain by using an unrealistic cognitive thought process and having expectations in life that are not possible to achieve. Whatever the cause, we are all at risk of having strong suicidal urges when it seems as though the future has become hopeless.

People know suicide is wrong so they start to think about it. People dont try to kill themselves until they lose all hope. They know there are other solutions but the pain becomes too great, and they try to deny the fact that in reality they want to live. The lonlyness and pain of whatever it is that caused the depression becomes unbearable.

A lot of the time it's because they are alone and they don't think anyone cares for them. But, also it seems that, many times, they read about it, or hear about and think about it over and over. News, friends, etc..Tell them about it, and sometimes they can't stop thinking about it.

Because not everyone loves their lives, and most feel all alone. Which is even sadder.