This one I struggle with. I believe in the right of self determination but I cannot help but ask the question "Have you tried..?" ..because mental can be cured for some. For others it is unassailable. The most natural course is to encourage someone with a mental condition to try these other things first, but I would not ask the same of someone with a physical condition, but with the brain we know very little.
It is a struggle between providing support for a person who has chosen to end their life, and not standing in their way should they ultimately choose to go forward.