A novel application of propensity score matching to estimate Alcoholics Anonymous' effect on drinking outcomes

Randomized controlled trials (RCTs) of mutual aid, including Alcoholics Anonymous (AA), are notoriously difficult to conduct and correlational studies are problematic to interpret due to potential confounds.

A secondary analysis was conducted of Project MATCH, a RCT of alcoholism treatments. Although MATCH did not randomly assign subjects to AA vs. no AA, the 12 step facilitation (TSF) condition did result in a higher proportion of subjects attending community AA meetings than in the other two treatment conditions. The key inference is that there exists a latent subgroup in MATCH who attended AA only because its constituents received TSF, not because of the "normal" factors leading to self-selection of AA. A novel application of propensity score matching (PSM) allowed four latent AA-related subgroups to be identified to estimate an unconfounded effect of AA on drinking outcomes.

The study hypothesis was supported: subjects who consistently attended AA solely due to their exposure to TSF (the "Added AA" subgroup) had better drinking outcomes than equivalent subjects who did not consistently attend AA, but would have so attended, had they been exposed to TSF (the "Potential AA" subgroup); this indicates an AA effect on drinking.

The analysis presents evidence that consistent AA attendance improves drinking outcomes, independent of "normal" confounding factors that make correlations between AA attendance and outcomes difficult to interpret.