I never really found being off the mind altering chemicals of this world for any length of time to be a cure. The problems that a person has that made them choose an altered mood lifestyle really do not go away. That would need to happen for a person to actually experience being cured in my opinion.
Rehab only gets you off the substances for the length of the program. When your rehab time is over, you still have the same chances of being drug free as one who quit on their own. A rehab reminds me of a long term paid rest that is very expensive.