I think there is a lot of truth in all of these answers.
I was raised by a strictly JW mother. Occasionally she would have a glass of wine with dinner, or one beer if we visited my nonJW grandparents.
I'd had severe depression and anxiety since at least the beginning of myteens, and at 15 was also diagnosed with post traumatic stress disorder. My doctor and I had a massive struggle to get my mother to allow me to take the antidepressants that I needed, and she still gave me a hard time about it constantly. (I wasn't praying enough and my faith needed to be stronger and I wasn't "relying on jehovah". All my problems would go away in the "new system", so I didn't need to worry about them now.)
When I was eighteen she married a man who was also JW and who is very abusive towards her.
Around this time I started drinking regularly. I would often sneak large quantities of alcohol into the house at night without my mother or that arsehole knowing about it.
Soon though, that wasn't numbing the pain enough. There was a family in the congregation whose house I used to hang out at a lotbecause I couldn't stand being at home, and because at the time I thought they actually gave a damn about me. I knew the brother had a regular supply of strong pain medication and I started finding excuses to ask him for it.
Soon after that I managed to escape the grip of the JWs and moved to the other side of town.
Suddenly I hardly knew anyone; the brainwashing was over and I was able to see that everything I had been taught my whole life was all lies; the aspects of myself that I had burried because they didn't fit with cult law could surface; I was constantly being guilt tripped by my mother; I was vulnerable because I had always been totaly sheltered and then when I was preyed upon my mother said it was because I had "turned my back on jehovah".
The level of my drinking increased and since I was not under constant supervision I started seeking out more drugs.