When these animals encounter acute stress, they can't cope. They become agitated, aggressive, or frustrated. Human prisoners have amputated toes, fingers, and genitals. I have deliberately omitted the lemmings. Acute psychiatric illness is the single most common and dangerous trigger of suicide.
Sleep loss tends to provoke mania in the manic-depressive.
Males are more likely to do it in most countries, BUT females predominate in Malta, Egypt, Papua New Guinea, western Ethiopia and China. Culture is clearly a factor. It is rare before the age of twelve. Seasonal variation is one of the most consistent findings in the literature. It isn't what you would expect.