It’s been a while since I reviewed the literature for substance abuse disorder, but if I remember correctly it was highly disputed whether complete abstinence was necessary (or even beneficial) for treatment. Has this changed?
The argument was that by focusing on abstinence you are setting a significant part of your patience up for failure with all the psychological harm involved in knowing that they’ve failed, which might result in severe and frequent relapses.
EDIT: To conclude. I find it hard to draw conclusions if success is measured in “days of abstinence”. That means that a patient that has recovered from cognitive behavior therapy (CBT) that uses occasionally and non-detrimentally is not considered a success! Further AA or other 12-step programs do often stress abstinence while CBT does not, this creates a counting bias in favor of 12-step programs.