Religious conversion is recognised as being one of the least effective methods of getting a person off drugs and/or alcohol. (For example, see Felix Donelly's Big Boys Don't Cry).
The ones boasted about in Afake Awake and Botchtower Watchtower as having kicked their drug or alcohol habits because of "The Truth" nearly always got back on the stuff sooner rather than later. I actually learned to drink from the brother that "brought me into the Truth".
(Sorry to have to report that I proved to be a very able student!)
Bill.