In order to determine whether the sites identified for the cannabis phenotypes were mainly due to comorbid alcohol dependence a separate linkage analysis was conducted using alcohol dependence as a covariate and few differences were found. The results of those analyses are presented in table 4. The linkage results for cannabis dependence, craving and withdrawal were also compared to the results obtained from previous linkage scans for alcohol and nicotine dependence that were also conducted in the UCSF family study population. None of the linkage regions reported in a previous linkage scan for alcohol dependence [Gizer et al., 2009] yielded neither significant nor suggestive linkage in a subsequent scan for nicotine dependence [Gizer et al., unpublished work] in the UCSF family study population. However, in the present set of analyses, suggestive evidence for linkage to cannabis dependence was found at a site on chromosome 2 previously identified in a scan for nicotine dependence [Gizer et al., unpublished work], and another site identified for cannabis craving on chromosome 9 in the present study was also identified in a previous scan for
