Which age group is most prone to senility or depression?

Depression has no age preference. It is a higher possibility in adolesence and the elderly, but can be in any age group. Senility is definitely in the elderly.

between ages of 17-25 id say they are prone to much more stress and less tolurent of it like adults are

I would say between like 13 and 21. I think that by 21 you should have overcome all that depression stage.

Can you pick one or the other? Because they are very different answers.