One thing I've heard a lot about mental illnesses is that you can't treat them very well unless the person believes and understands they have a problem. Otherwise, counseling is completely ineffective, and medication doesn't work either unless you can somehow force-feed it to them on a regular schedule (something you can only really do if they're institutionalized).
A frequently-cited problem with schizophrenics, for instance, is that they'll take some medication, feel much better, and then decide they're "better" and don't need medicine any more, and stop taking the medication, and then go back to nutty behavior.