since people are still talking about it, the
last rehab stat I researched was about fully randomized trial that contrasted AA with three other science-based treatment options and the all-important control group.
It's significant because it's one of the few trials where participants didn't self-select. e.g. many claims of AA's effectiveness are based on the number of long-term members who are abstinent, e.g. "80% of members have been sober for over 1 year". But only 5% of people who join AA last over 1 year. If you don't complete the program, they say you failed the program, not the program failed you, so you don't count. You're not constitutionally fit to do the program. AA's founder Bob Wilson claimed that they were born unfit to be cured. Since AA says alcoholism is a disease, imagine a medicine which failed to help 95% of patients then the doctor claimed the 95% of dead people weren't constitutionally fit to take the medicine, but the medicine works 100% of the time if you're up for it. That logic just does not fly when claiming your "method" is 100% effective and the only method.
Back to the scientific trials, AA did better than nothing by most measures, but not as good as getting actual treatment that's evidence based, and adapts itself based on research.
There was one area that AA did shockingly worse than all other options: binge drinking. AA members binge drank at 9 times the rate of those receiving professional interventions, and at almost 5 times the rate of those receiving no treatment at all. This is due to the AA ideology that if you have 1 sip of alcohol the drink will take over and it's not a choice - the disease is controlling you. And they literally have blood on their hands due to this. One stark example was a woman who quite publically switched from a program called Moderation Management which she had been on for over 10 years to the abstinence-based AA. Three months later, she binge drank and killed a father and son via drunk driving.