What sort of severe mental illness would require assisted suicide yet leave a person capable of informed consent? Differentiating suicidal ideation due to menta

What sort of severe mental illness would require assisted suicide yet leave a person capable of informed consent? Differentiating suicidal ideation due to mental illness from rational desire to die seems rather impossible. As for extreme pain, there is hospice. Calling assisted suicide medical care is so fraught with perverse incentives that it will certainly cause more harm than good.