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. There is greater seasonality in rural areas than in urban ones. Lithium is more effective than other antidepressant. Experts report that when antidepressants are found in the bloodstream, they are usually at too low a level to be clinically effective. Siblings feel terrible pain, but studies suggest that relatively few have long-term adverse psychological consequences.