The most notable finding from this report on DSM-IV Nicotine Withdrawal (NW) is a linkage signal (LOD = 3.6) that meets genomewide significance on chromosome 11p15 in the Finnish families. Smaller signals in the same area on 11p15 were detected in the same Finnish sample using binary phenotypes for DSM-IV nicotine dependence (ND) and FTND using two-point non-parametric linkage (LOD = 1.8; Loukola et al., 2008), which is consistent with the modest to high correlations we found between DSM-IV NW and DSM-IV ND and DSM-IV NW and the FTND in this same Finnish sample. Maximum cigarettes in 24-hours (Saccone et al., 2007a) and other quantitative measures of nicotine dependence did not show linkage on chromosome 11p15 in these samples. This pattern of findings suggest that there may be genetic variation influencing nicotine withdrawal that is not easily detected using other measures of nicotine dependence (including DSM-IV-based nicotine dependence), especially in the Finnish sample. While bivariate linkage analysis using both FTND and DSM-IV NW might illuminate common versus specific genetic effects, the small number of NW-affected Finnish sib-pairs available precludes this approach.
