There are several strengths of this study. The sample is based on 1,923 individuals from 219 extended families, with a wealth of reliable and valid information obtained on each individual through the well-characterized SSAGA (Bucholz et al., 1994; Hesselbrock et al., 1999). This large sample was limited to European-Caucasian, non-Hispanic families, thus limiting heterogeneity of the haplotypes used in analyses. The use of family-based association tests reduced potential confounding from population stratification. Finally 39 SNPs were genotyped across NPY and its three receptor genes on chromosome 4, NPY2R, NPY1R, and NPY5R, all with moderate LD to establish extensive coverage of all genes.
