Family based association analyses were performed using the Pedigree Disequilibrium test (PDT) (Martin et al., 2001) as implemented in the program UNPHASED (version 2.404) (Dudbridge, 2003). The PDT uses data from all available trios in a family, as well as discordant sibships. The PDTsum statistic, which gives greater weight to families with a larger number of informative trios and discordant sibships, was utilized as the primary statistic. Haplotypes from phase-certain individuals were used to further explore significant associations across the GABRR1-GABRR2 gene cluster. Association analysis using the haplotypes was performed using UNPHASED and the PDTsum statistic.
