Background: The current analysis applies clinical significance methodology to alcoholism treatment outcome research using data available from Project MATCH. Because of its high internal validity and its inclusion of multiple measures assessing multiple outcome dimensions, MATCH was considered an ideal study to explore the utility of this methodology.
Methods: Data reported here are from a total of 1,726 participants enrolled in either aftercare (n = 774) or outpatient (n = 952) arms of the study. First, a cutoff score was determined differentiating functional versus dysfunctional status on three outcome measures: percent days abstinent (PDA), mean drinks per drinking day (DDD) and negative consequences of alcohol use. Second, the reliable change in pre- to post-treatment scores on these three measures was calculated.
Results: The results reported herein support the importance of distinguishing between statistical and clinical significance of outcomes. During three months post-treatment, approximately one-half of the treated patients were "recovered" (i.e., both functional and reliably changed) with respect to both PDA (i.e., 51%) and negative consequences of drinking (i.e., 47%); however, only about one-third of individuals remained recovered throughout the full one-year follow-up period (i.e., 33% on PDA and 35% on negative consequences). These individual-based change outcomes compared similarly to a population-based indicator of heavy drinking. Alternatively, only about one-quarter of participants were recovered using two distinct criteria for mean DDD (i.e., 23-29%), and even fewer participants remained recovered on mean DDD over the full one-year follow-up period (i.e., about 14-18%).
Conclusions: Based on study limitations, more work is required to make clinical significance methodology practically useful to alcoholism treatment trials including more precise definitions of functional status and relative change as well as better interpretation of the inter-relationship between multiple measures assessing multiple outcome domains.