Validity of self-report drug use among people with co-occurring mental health and substance use disorders

Objectives: The validity of self-reports of drug use from individuals who abuse substances has been questioned. Results from studies examining the accuracy of such self-reports have been mixed, indicating the need for closer examinations of the factors associated with concordance between self-reported drug use and results of urine screens. Methods: As part of a larger study examining the effectiveness of interventions for people with co-occurring mental health and substance use disorders, we examined the agreement between self-report and urine screens for recent drug use. Results: Overall, the concordance between self-report and results from urine screens was high (80-84% agreement overall and 75-79% for the subset where the urine screen indicated recent drug use). Estimates for the likelihood of use of marijuana and cocaine within the past 30 days were 15% and 32%, respectively, based on urine screens, 25% and 35% based on self-report, and 28% and 43% based on information from both sources combined. About 1/3 of individuals who had at least one positive urine screen misrepresented their drug use at least once. Such misrepresentation tended to increase with time in the study. Conclusions: The relatively high concordance rates between selfreport and urine screens indicate that situations can be structured so that individuals with co-occurring mental health and substance use disorders report instances of substance use accurately most of the time. Given the observed increase in failure to report use through time, the utility of biological markers may be more valuable as clients develop relationships with clinicians. (Author' s abstract)