Notably, there was no evidence of heterogeneity in LOD scores across pedigrees as each family had an estimated alpha, interpreted as the probability of a given family belonging to a single population yielding evidence for linkage, that was >0.99 for each peak as estimated by the SOLAR HLOD function (Goring, 2002). Linkage analysis of the 14 nicotine dependence symptoms assessed by the SSAGA across the support interval of this peak (181–192 cM) showed that the symptom ‘thought a lot about quitting or cutting down’ yielded the strongest evidence for linkage (LOD = 2.66). The symptoms ‘tobacco had less effect with continued regular use’ (LOD = 1.74), ‘found self smoking more than intended’ (LOD = 1.45), and ‘continued to smoke despite tobacco-induced emotional problems’ (LOD = 1.05) also appeared to contribute to the observed linkage peak (see Table 2 for complete results).
