This cluster analytic approach may also be useful in identifying etiological relationships between disorders. As an example in this study, the numbers of DSM-III-R anxiety and affective disorders did not differ between heritable and non-heritable subtypes of cannabis dependence. This finding is consistent with a previous finding in this sample that cannabis dependence was not co-morbid with anxiety and affective disorders (Gilder et al. 2006). Taken together, these findings suggest that anxiety and affective disorders may not be as etiologically related to cannabis dependence in this population as they may be in other populations where co-morbidity is more pronounced (Regier et al. 1990; Grant 1995; Grant & Pickering 1998; Agosti et al. 2002).
