There is no easy answer to that. We know that treatment that is non-coerced tends to be more effective, tends to help people if they recognize that they have a problem and want help with it.
That having been said, there are provisions in the law, of course, for treatment without consent under very limited circumstances. In the code, it's in order to make someone fit to stand trial, and those are the only circumstances in Ontario in which you can treat someone, under the law, without their consent. It's a basic human rights issue.