al., 2011; Moore and Budney, 2001), although evidence is less consistent on whether they demonstrate poorer tobacco treatment outcomes than individuals who use tobacco only (Abrantes et al., 2009; Ford et al., 2002; Gourlay et al., 1994; Haskins et al., 2010; Hendricks et al., 2012; Metrik et al., 2011; Patton et al., 2005; Stapleton et al., 2009). The high prevalence of psychiatric disorders found in this study may serve as a potential explanation of the trend towards poor treatment outcomes for adults with co-occurring cannabis use disorders and nicotine dependence. Psychiatric disorders signify impaired functioning in multiple domains of functioning (e.g., interpersonal relationships, cognition), and these impairments may interfere with the provision of treatment to individuals with co-occurring cannabis and tobacco use. For example, maladaptive personality functioning could interfere with the provision of substance abuse treatment through its contribution to premature drop-out (Ball et al., 2006). Future studies with individuals with co-occurring cannabis use disorders and nicotine dependence can investigate how the presence of psychiatric disorders interacts with treatment to affect outcomes.
