Our FBAT analyses focused on a subset of common tagging SNPs at the OPRM1 gene and therefore it is possible that we did not include OPRM1 SNPs that may contribute to the nicotine withdrawal sensitivity score phenotype. In our study we employed the use of tagging SNPs and eliminated non-informative SNPs from analysis in order to reduce the likelihood of false associations due to multiple testing. Further examination of OPRM1 variation through use of haplotype analyses, and through analyses of less common and rare variants, in relation to the nicotine withdrawal sensitivity score should be pursued in SMOFAM and additional samples.
