Subtyping of substance dependence disorders holds promise for a number of important research areas including phenotyping for genetic studies, characterizing clinical course, and matching treatment and prevention strategies. This study sought to investigate whether a dichotomous construct similar to Babor’s Types A/B and Cloninger’s Types I/II for alcohol dependence can be identified for cannabis dependence in a Native American sample. In addition, heritability of this construct and its behavior in a genetic linkage analyses were evaluated. Information on cannabis use and dependence symptoms and other psychiatric disorders was obtained using the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) from a community sample of 606 American Indians. Hierarchical average linkage and K means cluster analysis was used, and a 3-cluster solution was found to generate the best separation of variables. Ninety-one percent of cannabis dependent participants fell into one of the two subtypes: Type A/I cluster (N=114, 56%) and Type B/II cluster (N=70, 35%). Heritability (estimated using SOLAR) was only significant for the Type B/II cluster (h2 =0.44, S.E.=0.18, p 1.5) were also located on chromosomes 14,21,22. These findings suggest that a Type B/II cannabis dependence phenotype can be identified in this population and that it is in part heritable and linked to areas of the genome identified previously for drug dependence phenotypes in this population as well as in other studies
