Depression IS an illness, you kind of separate it out from the other illnesses in your post. Your partner is in the throes of an illness that can take a life like a cancer can.
When we get sick (with whatever illnesses) we do/say/don't do/don't say things that could/should preferably get done/said. We act in ways we never would if we weren't sick and hurting from the pain and symtoms of the illness. My partner has had to prop me up with this insideous illness multiple times for multiple years...just like when I wasn't sick, I propped up my partner when stuggling with work or grad school or kids etc. It is kinda what a relationship is about imo.Sorry if I am preaching.