Id argue depression could be. At least with cancer and other illnesses, some can get a renewed love of life and appreciation for the small things. Wishing for death and never feeling happy is just unbearable. I’d rather get cancer and have only five more years to live happily then be terribly depressed for another 50. The other thing is you have no desire to do anything except sleep and drugs. No ambitions, no purpose, at least if you know you will die, you start working toward making those years count. You can’t even make a lifetime count and even if you could you wouldn’t be happy doing so with depression.