The variance components approach to linkage incorporates information from affected and unaffected participants by estimating linkage across the entire pedigree (Almasy & Blangero, 1998), and has been shown to possess comparable statistical power compared to relative-pair based methods (i.e., Kong and Cox statistic (1997)) for both quantitative (Amos et al., 1997) and dichotomous phenotypes (Duggirala et al., 1997). Thus, the variance components approach implemented in SOLAR was used to calculate multipoint LOD scores across the genome at 1 cM intervals for DSM-IV nicotine dependence. Peaks that achieved a LOD score greater than 1.0 were reported as regions of interest as suggested by Lander and Kruglyak (1995).
