Assisted suicide is only ethical (Where applicable) when the person is on the verge of death and hastens it. In most cases the person is in severe pain and needs relief, and hastening their demise can be viewed as merciful. It is not intended to be used to legally assist someone who just doesn't want to live any more.

Myself, I think AS should be allowed in cases of severe pain at the end of a terminal illness.

This is a controversial issue, as no one can really say if the person will die of the illness for sure. Spontaneous remissions happen all the time, sometimes even on one's death bed.

Again, AS, legal or not, is not intended to help mentally ill patients commit suicide.