Within-treatment frequency of use versus abstinence as a predictor of longitudinal post-treatment follow-up assessments of drug use.

Abstract

Abstinence is a widely-used endpoint in clinical trials of stimulant use disorders. A quantitative measure of frequency of use may be a more sensitive endpoint; however, it is important to establish that it is associated with post-treatment drug use. We examine and compare how within-treatment abstinence and frequency of use are related to two post-treatment longitudinal measures of drug use. For each of three existing stimulant use disorder clinical trial datasets, we examined the association between within-treatment frequency of use (based on urine screens), within-treatment abstinence, and post-treatment follow-up assessments of drug use (urine screens and reported days of use). In joint analyses that simultaneously model the effects of within-treatment abstinence and frequency of use, it is possible to discern their relative importance as predictors of post-treatment drug use during the 12 months following the end of treatment. Results indicate a quantitative measure of within-treatment frequency of use was associated with longitudinal post-treatment follow-up assessments of drug use. Results from joint analyses of post-treatment follow-up drug use assessed by urine screens suggest that within-treatment frequency of use, rather than abstinence per se, is predictive of post-treatment drug use. However, results from joint analyses of self-report of days of use are equivocal. Results lend support to the use of a quantitative measure of within-treatment drug use as an alternative to complete abstinence. They suggest that some within-treatment use that fall short of complete abstinence may potentially represent clinically important improvements given their association with post-treatment drug use.