this topic touches me particularly, both because i've had my own background in substance use & abuse, and because one of my dearest brothers in Christ that i've known for 30 years is right now serving a prison sentence for making meth in his home. he was addicted. he's struggled with addictions to various things his whole life, and from the time he accepted Christ at a very young age till the present, he's also followed Him and believed and never rejected the faith, though he may stray. i never considered him 'not a Christian' -- though his behavior, like all of ours, was sometimes very un-Christ-like.
God has been using his arrest and prison term in a very profound way to draw him back to Himself, to help sanctify his life, and to remove these entanglements in his flesh. it is the answer to many prayers, and he sees it this way too. we both bless God for this! for this man, it took this shocking and troubling circumstance to get through his thick skull. we thank God that it didn't take death! as it does finally for some others.
the Lord chastises and teaches His sons and daughters. we don't cease to become His children because He is reproving us -- it makes us all the more His children; it is evidence.