Two single-site GWAS and two multi-site (consortia-based) meta-analysis GWAS studies have been unable to detect genome-wide significant associations with cannabinoid use disorder (Haughey, Marshall, Schacht, Louis, & Hutchison, 2008b; Lind et al., 2008a; Stringer et al., 2016; Verweij, et al., 2012). A recent GWAS meta-analysis using 13 study sites and a sample size of over 32,000 participants identified no significant SNP-level associations, but significant gene-based associations between lifetime cannabis use and NCAM1, CADM2, SCOC, and KCNT2 were detected. Of these, NCAM1 has been best characterized and is part of the NCAM1-TTC12-ANKK1-DRD2 gene cluster, which is related to neurogenesis and dopaminergic neurotransmission (Stringer, et al., 2016). The functional significance of the products of the remaining genes are largely unclear and encourage further investigation (Table 4).
