SCN9A and nicotine dependence: While the majority of genes identified in the included studies had either no known function or biological plausibility, and none had any additional associations with cannabis use, as mentioned above, several did have associations with mental health conditions and are discussed briefly, namely ANKFN1, INTS7, PI4K2B, CSMD1, CST7, ACSS1, and SCN9A. ANKFN1 is a protein coding gene which has been associated with smoking cessation and nicotine dependence [31].