Rates and influences of alcohol use disorder comorbidity among stimulant-primary treatment-seekers: Meta-analytic findings across eight NIDA CTN trials

The United States has seen serial pandemics of stimulant misuse. The 1980’s marked a rise in cocaine use, whereas subsequent decades saw a rampant spread in amphetamine use [1]. Estimates suggest 40 million cocaine and amphetamine users worldwide [2], and monthly prevalence of cocaine and amphetamine use in the U.S. alone of 2.4 % and 1.2%, respectively [3]. Absence of FDA-approved pharmacotherapy for stimulant misuse heightens need for effective treatments and support services. To that end, identifying rates of substance-related comorbidity—like prior or concurrent alcohol use disorders (AUDs)—may inform clinical service needs. Because problem drinking, or the prospect of its occurrence, may diminish psychosocial functioning of stimulant-misusing clients and thereby hamper treatment effectiveness, determination of AUD rates for amphetamine- and cocaine-misusing treatment-seekers is salient. By comparing psychosocial functioning of stimulant misusers with and without AUD, we may inform tailoring of their clinical services. Reviews of treatment process and response suggest much similarity between cocaine and amphetamine misusers [4, 5], and recent treatment trials aggregate them analytically [6-8] despite limited evidence of homogeneity in pre-treatment characteristics. Two single-site trials document predominance of males (60-82%) [4, 5], though rates vary between substances and trials. In each trial, race distinguished amphetamine and cocaine misusers, with the former comprised largely of Caucasians (72-80%) and latter by more balanced racial heterogeneity. Comparisons of other demography (e.g., age, marital, employment status) are equivocal. Copeland and Sorenson [4] do note greater proportion of amphetamine misusers as gay or bisexual than cocaine misusers, as well as their greater likelihood of medical complications, high-risk drug practices, psychiatric comorbidity, receipt of psychiatric medications, and prior suicidality. AUD comorbidity may impact psychosocial functioning for both amphetamine and cocaine misusers, with concurrent AUD diagnoses serving as risk factors for emergence of future alcohol problems, stimulant relapse, and other forms of treatment noncompliance. Extant literature suggests these groups differ in several psychosocial indicators, suggesting prospective analyses of these groups be stratified by stimulant type. In contrast to single-site trials, multi-site trial designs may offer more powerful and informative comparisons of treatment-seeking groups due to larger, more representative client populations typically enrolled [9]. Presumably, this methodological strength would be amplified by aggregating treatment-seeking samples of interest across multiple multi-site trials. With respect to this report, such aggregation may allow more meaningful examination of influences of AUD comorbidity on psychosocial functioning for amphetamine and cocaine misusers. NIDA’s Clinical Trials Network [CTN; [10]] provides a vehicle for such examination, as it has for over a decade tested promising innovations via multi-site trials in community treatment agencies. With nearly three dozen such trials completed or underway, CTN invites use of its existing databases for secondary analyses. Its routine pre-treatment administration of a diagnostic instrument for substance use disorders (e.g., DSM-IV Checklist, CIDI 2.1) as well as a broad range of psychosocial functioning indicators on the Addiction Severity Index – Lite [11-13] across treatment trials offers a unique resource for our comparisons of interest. This report documents our continued work on a CTN-approved secondary data analysis study examining pre-treatment client characteristics across trials [14]. The target of this report is treatment-seekers for whom stimulants (e.g., cocaine, amphetamine) are the primary substance of misuse. An initial aim was to describe pre-treatment rate of alcohol use, AUD diagnoses, and related phenomena in subgroups of primary stimulant misusing treatment-seekers. Further aims involved paired comparisons of the influence of AUD comorbidity (e.g., primary amphetamine misuser with AUD vs. without AUD, primary cocaine misuser with AUD vs. without AUD) on psychosocial functioning. Consistent with extant literature, higher rates of alcohol use, AUD diagnoses, and related phenomena by primary cocaine misusers were anticipated, whereas more pronounced psychosocial difficulties were expected of primary amphetamine misusers. Further, both primary stimulant with AUD subgroups were expected to evidence poorer psychosocial functioning than primary stimulant without AUD counterparts. A supplemental aim of the report is to discuss methodological issues and challenges encountered in this trans-protocol examination of CTN data.