We have performed the largest meta-analysis to date of GWASs investigating cannabis use phenotypes. With a sample of over 32 000 individuals, our results implicate four genes as involved in lifetime cannabis use: NCAM1, CADM2, SCOC and KCNT2. Our results illustrated that lifetime cannabis use is under the influence of many common genetic variants. The combined SNPs explained 13–20% of the phenotypic variation, and revealed a high degree of genetic sharing (r=0.83) with lifetime cigarette smoking. Future studies should investigate the impact of these genes on the biological mechanisms leading to lifetime cannabis use.
