Cannabis use is common, but most users do not progress to cannabis use disorders. About 50–70% of liability to cannabis use disorders is due to genetic factors.1 Three genome-wide association studies (GWASs) of cannabis use disorders2, 3, 4 have identified variants reaching genome-wide significance, but inadequate sample sizes (sample size from largest study to date: 51 372, with 2387 cases) and heterogeneity among samples have contributed to a paucity of replicable findings: only one locus, tagged by a cis-eQTL for CHRNA2 (encoding a nicotinic acetylcholine receptor), has been robustly identified.3
