Cocaine abusers with and without alcohol dependence respond equally well to contingency management treatments.

Among individuals with cocaine use disorders, reports of comorbid alcohol dependence (AD) range as high as 57-88% (Higgins, Budney, Bickel, Foerg, & Badger, 1994; Wiseman & McMillan, 1996). Alcohol's perceived enhancement of cocaine's rewarding effects (Harris, Everhart, Mendelson, & Jones, 2003) and/or attenuation of adverse effects, including withdrawal (McCance-Katz, Kosten, & Jatlow, 1998), may at least partially explain the high rates of concomitant cocaine and alcohol use. Not surprisingly, comorbid use of these substances is associated with more severe cocaine use (Mengis, Maude-Griffin, Delucchi, & Hall, 2002; Raimo, Smith, Danko, Bucholz, & Schuckit, 2000) and more negative consequences related to cocaine use (Flannery, Morganstern, McKay, Wechsberg, & Litten, 2004; Higgins et al., 1994b). The impact of cormorbid alcohol and cocaine disorders extends to areas of psychosocial functioning, including greater alcohol-related problems, family-related difficulties, and psychiatric severity (Flannery et al., 2004; Higgins et al., 1994b; Schmitz, Bordnick, Kearney, Fuller, & Breckenridge, 1997). Despite these negative consequences, comorbid cocaine and alcohol use disorders do not necessarily detract from treatment outcomes. Neither baseline alcohol consumption, nor alcohol severity scores, predict sustained or point-prevalence abstinence from cocaine among individuals with cocaine use disorders completing 12-step or cognitive-behavioral outpatient group substance use treatment (Crits-Christoph et al., 2007; Mengis et al., 2002). Carroll, Rounsaville and Bryant (1993) noted similar 1-year posttreatment abstinence rates, as well as posttreatment cocaine use intensity, for cocaine dependent versus cocaine-alcohol dependent individuals following community-based inpatient or outpatient substance abuse treatment. Similarly, individuals with cocaine dependence achieved significant reductions from baseline cocaine use, regardless of AD status, following either relapse prevention or 12-step substance use treatment (Brower, Blow, Hill, & Mudd, 1994; Schmitz et al., 1997). Benefits of treatment extend to areas of psychosocial functioning for cocaine dependent individuals regardless of concurrent AD, with comparable posttreatment Addiction Severity Index (ASI) medical, employment, and psychiatric scores (Brower et al., 1994). Similarly, Schmitz et al. (1997) noted improvements in psychiatric symptomatology over the course of treatment for both diagnostic groups, although individuals with cocaine-alcohol dependence evidenced greater severity at each assessment point compared to those with cocaine dependence. Heil, Badger, and Higgins (2001) examined treatment response of cocaine dependent individuals with and without AD who received either community reinforcement approach (CRA) therapy plus contingency management (CM) or one of four comparison conditions. CM is well established as an effective treatment for reducing cocaine use (see Lussier, Heil, Mongeon, Badger, & Higgins, 2006; Prendergast, Podus, Finney, Greenwell, & Roll, 2006). CM involves restructuring the environment to promote target behaviors (e.g., abstinence), typically through reinforcement using vouchers or prizes contingent upon verified achievement of target behaviors (Higgins, Budney, Bickel, & Foerg, 1994; Stitzer & Petry, 2006). Unlike the studies discussed above, Heil et al. (2001) observed treatment by AD status interactions on treatment outcome. While individuals with cocaine-alcohol dependence had shorter treatment retention in the comparison conditions compared to those without AD, they stayed in treatment longer than those without AD when assigned to the CRA plus CM condition. For abstinence outcomes, the cocaine-alcohol dependence group submitted a greater proportion of cocaine negative samples compared to the cocaine dependent only group when treatment involved CRA plus CM. Abstinence rates were similar regardless of AD status in the comparison conditions. Although the literature assessing the impact of AD on treatment outcomes among cocaine abusers is small, the available studies generally failed to identify treatment by AD status interaction effects with the exception of the Heil et al. (2001) study. The Heil et al. (2001) study was distinct from other published studies in the use of CM, which may account for the noted difference in treatment condition by AD status interactions. However, the ability to attribute these interaction effects to CM is limited; the observed improvements in retention and abstinence for cocaine-alcohol dependent participants may have been due to the combined use of the CRA with CM, rather than attributable to the effects of CM alone. Another possible contribution to the significant interaction effect in the Heil et al. (2001) study involves differences in use of disulfiram (included as part of CRA) across conditions. Participants in the control conditions were less likely to take disulfiram, perhaps explaining the poorer outcomes for AD participants in the control conditions for the Heil et al. (2001) study. The purpose of the present study is to assess the impact of AD status on primary and secondary treatment outcomes for cocaine abusers receiving standard care as delivered in community-based treatment programs with and without CM. This study will aid in clarifying the impact of AD status on response to CM and standard care treatments. Specifically, the present study tested the hypothesis that CM treatment may be more beneficial than standard care for cocaine abusers with AD. To this end, we examined abstinence-related outcomes and psychosocial adjustment according to AD status and treatment condition at two timepoints, end-of-treatment and a Month 9 follow-up. Consistent with the primary study findings (Petry et al., 2004; Petry, Alessi, Marx, Austin, & Tardif, 2005; Petry et al., 2006a), an overall benefit in treatment outcomes was expected for those assigned to CM compared to standard care. Given the Heil et al. (2001) findings, we predicted a potential significant interaction effect between AD status and treatment condition. We hypothesized that AD participants would achieve improved abstinence-related and psychosocial outcomes compared to non-AD participants when assigned to CM, and we predicted comparable outcomes across AD status groups for those assigned to standard care. We examined long-term effects using objectively-verified abstinence at the Month 9 follow-up and posttreatment change in ASI scores. We hypothesized that long-term abstinence rates would not differ by AD status, and any gains achieved in ASI scores during treatment would be maintained through the follow-up period.