Exclusion criteria in treatment research on alcohol, tobacco and illicit drug use disorders: A review and critical analysis.

Abstract

High rates of exclusion in substance use disorder treatment studies reduce the external validity and clinical utility of research findings to an unknown extent. Accordingly, the current review examined commonly used exclusion criteria and their effect on study samples and outcomes. English-language literature was identified by PubMed searches and review of identified articles' reference lists. Studies were included if they analysed data on: (i) the prevalence and nature of exclusion criteria in the substance use disorder treatment field; and/or (ii) the impact of exclusion criteria on sample representativeness or study results. The search yielded 22 studies examining different aspects of exclusion criteria, including 15 empirical examinations of the impact of study exclusion criteria across different substance use disorder treatments on enrolment and outcome results. Aggregating across these 15 studies, we estimated that between 64 and 96% of potential study participants are excluded from substance use disorder treatment studies. The widespread exclusion of large proportions of people with substance use disorders limits the external validity of the substance use disorder treatment research literature. Although some eligibility criteria are necessary to protect participant safety and ensure internal validity, researchers conducting studies on substance use disorder treatments should thoughtfully consider the justification for and specific operationalisation of the extensive exclusion criteria they often utilise. [Moberg C, Humphreys K. Exclusion criteria in treatment research on alcohol, tobacco and illicit drug use disorders: A review and critical analysis. Drug Alcohol Rev 2017;36:378-388].