Secondary analyses were conducted in order to determine whether these genome locations were specific only to the “nervous, tense, restless or irritable” symptom of withdrawal or whether the “sleeplessness” and a “number of withdrawal symptoms count” phenotype could also produce similar LOD scores in those locations. Evidence for linkage on chromosome 9 was found for the “sleeplessness” phenotype at 158 cM (LOD = 4.2) and the symptom count phenotype (LOD = 3.2). Additionally, suggestive evidence for linkage for the sleeplessness (LOD = 2.6) and symptom count (LOD = 3.0) phenotype was found on chromosome 3 with a peak at 95 cM. Thus it appears that similar regions in the genome may harbor genes for several withdrawal symptoms.
