These twin studies have provided an important first step towards our comprehension of the etiology of cannabis use disorders by demonstrating the existence of heritable influences on these outcomes. However, the genetic influences estimated in these models refer to latent or unmeasured genetic factors that presumably represent the composite variance explained by hundreds of individual genes, without identifying any specific genes. There are several current efforts underway that have begun to scan the genome for regions, genes and variants in genes that influence the liability to develop cannabis use disorders. Several genomic strategies exist, the more common ones being genomewide linkage analysis, genomewide association analysis and candidate gene association analysis.
