Samples included in the current study were ascertained for DSM-IV cocaine or opioid dependence (linkage sample), and AD (SAGE), and CD, OD or AD (in the replication sample). Therefore, the linkage and association signals detected for CaD in AAs could be attributable to other substance dependence (SD). We examined this alternate explanation for the findings in several ways. First, we examined the linkage signals across other SD traits (AD, CD, OD, and nicotine dependence (ND)) in the same family dataset (Supplementary Figure 2). The only linkage signal that we found with a lod greater than 1 in the chromosome 8 region reported above for CaD was a modest signal (lod = 1.4) for ND at 41 cM (i.e., ~14 cM away from the CaD linkage peak). Second, we tested the association of rs17664708 with other SD in each AA sample and the joint datasets (Supplementary Table 2). In the joint analysis, we observed highly significant associations between rs17664708 and CD (P=0.0023), AD (P=0.0076), ND (P=0.0026) and OD (P=0.00018). However, significant associations disappeared when subjects affected with CaD were excluded from
