Treatment may influence self-report and jeopardize our understanding of outcome

Standardized measures of self-reported alcohol use are the predominant method by which change in alcohol use following interventions is evaluated. This study examined whether the invariance of the test-retest pretreatment Alcohol Use Disorders Identification Test (AUDIT) was affected by the treatment experience. In this study, the intervening exposure was to motivational interviewing (MI) versus community service (CS), the treatment-as-usual control group.

Analyses were conducted on a subsample of court-referred 16- to 21-year-olds recruited into a randomized controlled trial examining the effects of MI on alcohol use and police charges for risky driving and/or drinking. Youths were randomized to CS or MI. A subsample of 478 participants, who at baseline completed the AUDIT in reference to alcohol use for the 6 months before their conviction, later repeated the AUDIT at treatment completion, in reference to the same 6-month baseline period.

At completion of treatment, participants receiving CS had a significant decrease in baseline AUDIT scores, whereas those in MI reported no significant change. The difference between the two groups was significant (p = .02). Also, of those who reported no drinking before treatment, after receiving MI, 33.5% changed their response and acknowledged pretreatment drinking, compared with only 8.3% in CS.

These results suggest that treatment received may differentially affect a standardized measure of self-reported risky drinking. This effect may be attributable to the treatment experience and/or the experience of the control group. Possible explanations for the effect are explored, including more honesty because of a trusting therapeutic alliance and a response shift bias. Differential change in self-report might affect treatment outcome assessment. Depending on the treatment contrasts, research that relies on pre- to post-treatment changes in self-report may be underestimating treatment effects.