Furthermore, all of these genes have shown some degree of association with externalizing phenotypes or neuropsychiatric disorders in other studies, although the strength of the evidence varies. Of note, one SNP in CSMD1 showed genome-wide significance in a large GWAS study of cannabis dependence (Sherva et al., 2016), and SNPs within CSMD1 were associated with tobacco use cessation in a clinical trial (Uhl et al., 2008). Similarly GABRR2 was associated with alcohol dependence in a sample (N = 1000+) with family history of alcohol use disorders (Xuei et al., 2010). Three genes, CSMD1, GRID2 (Greenwood et al., 2016), and GABRR2 (Wang, Liu, & Aragam, 2010) have also been associated with schizophrenia or bipolar disorder in moderately large samples (N = 1000+). Potentially related to behavioral self-control or reward processes, LINGO2 is associated with body mass or obesity (Rask-Andersen, Almén, Lind, & Schiöth, 2015), as is MARCH1 (Lee et al., 2016). Lastly, there is preliminary evidence of association between variants in GABRR2 and general cognitive ability (Ma et al., 2016) in a moderately sized (N = 987) Han Chinese sample. The
