with either conduct disorder or suicide attempts results in a maximum LOD score of 5.4 in the centromeric region of chromosome 2. Although the joint phenotype of AD or CD or SUI produced a similar LOD score in the microsatellite linkage analyses, the allele sharing was considerably lower, and in the SNP linkage scan, the LOD score was considerably lower. One hypothesis for this pattern of results is that limiting analyses to the AD individuals with CD or SUI yielded a more homogeneous group with a more heritable, behaviorally disinhibited phenotype. Not only is AD more narrowly defined by this joint phenotype, so might be SUI. By requiring at least some of the suicide attempts to be comorbid with alcohol problems, we may have largely retained “externalizing” attempts and eliminated attempts that reflected planned, internalizing-based behavior. The subset of AD individuals in the association sample who also met criteria for conduct disorder or a suicide attempt were a more severe subset of the cases by a number of criteria: they were more likely to meet criteria for an illicit drug dependence diagnosis (77.1% vs. 51.5%, P <0.001), had a higher mean number of illicit drug dependence symptoms (12.10, SD =
