By means of genetic linkage and association studies it could be possible to identify some of the specific genetic variants that influence cannabis use. However, cannabis use phenotypes are likely to be polygenic, with each gene accounting for only a small proportion of the variance, as seems to be the case for other complex phenotypes (63). For substance use disorders in general, genome wide association studies have found dozens of genes that could contribute to vulnerability (64). Many of these gene variants are likely to alter specification and maintenance of neuronal connections (64). Genes identified as affecting vulnerability to drug use problems could be potential targets for pharmaceutical drugs aiming to modify addictions.
