Several studies suggest that there is a moderate genetic influence on cannabis dependence and recently there have been several reports that have identified regions in the genome that may be linked to cannabis dependence (Kendler & Prescott 1998; Tsuang et al. 1998; Maes et al. 1999; Miles et al. 2001; Lynskey et al. 2002; Kendler et al. 2003; Rhee et al. 2003; Wilhelmsen & Ehlers 2005; Agrawal & Lynskey 2006; Hopfer et al. 2007; Agrawal et al. 2008). Hopfer and colleagues (2007) conducted a genome wide scan for loci influencing adolescent cannabis dependence in 324 sibling pairs from 192 families. In that study, probands (52.1% of whom were EuroAmerican, 36.5% of whom were Hispanic, and 7.8% of whom were African-American) were identified from consecutive admissions to substance abuse treatment facilities. The authors found evidence for suggestive linkage on chromosomes 3q21 (LOD = 2.61) and 9q34 (LOD = 2.57). These areas of the genome were not identified in the current linkage scan for Cannabis dependence II/B, however, a region on chromosome 3 was previously identified in a genome-wide linkage analysis for
