Seriously? Is the world really that apathetic? Disgusting.
How can people care so little about the mental health of people with self-destructive tendencies?
Then you stop it. Go ahead, we'll wait here.
Climb off your high horse. It sure as hell isn't as easy as you make it sound. It's not like turning off a valve. Human beings are incredibly complex, both psychologically and physiologically. There is no wonder cure. It's probably always going to exist as long as people have emotions, to be honest, and our mental states are ruled by chemical processes.
Ultimately, a person only has control over themselves. The best you can do is try to convince them see things differently. Even then, we all have our own demons, our own problems, our own tragedies, and there certainly isn't a magic fix for all of them.