Although many linkage scans have been reported for addiction to a specific drug, only few have investigated the convergence of linkage peaks across drug addictions. Toward this objective, we searched for linkage peaks among multiple abused substances, according to the criteria proposed by Lander and Kruglyak.34 We found that regions on chromosomes 2–5, 7, 9–11, 13, 14, and 17 have independent evidence of “suggestive” or “significant” linkage, with regions on chromosomes 4, 5, 9, 10, 11, and 17 receiving the strongest support for harboring susceptibility genes for addictions to multiple drugs (Figure 1).
