Several studies have sought to identify specific genetic risk factors associated with cannabis use phenotypes. Genome-wide linkage studies have revealed suggestive evidence for linkage across many chromosomes.16, 17, 18, 19, 20 With very little consistency across studies, nearly all findings failed to meet genome-wide significance. The one study examining lifetime cannabis use16 reported a nonsignificant linkage locus on chromosome 18 (LOD score=1.97).
