It says something about our culture that suicidal urges are considered something that need to be "treated". From a logical point of view it is the decision to continue to exist that needs to be justified, simply because it is the positive performance of actions (gathering life sustaining resources etc). The suicidal person should flip the question on its head and ask the nonsuicidal person what's their justification for living.
This is like asking the question, why are people poor? Ever since Adam Smith we know that poverty is the natural state, that what needs to be explained is abundance.
This is like asking the question, why are people poor? Ever since Adam Smith we know that poverty is the natural state, that what needs to be explained is abundance.