Genome-wide data were collected using blood samples obtained at the age 22 assessment. Genotyping was performed at the Welcome Trust Sanger Institute (Hinxton, UK) on the Human670-QuadCustom Illumina BeadChip (Illumina, Inc., San Diego, CA, USA), as previously described in Broms et al. (2012). The data were checked for MAF >1%, genotyping success rate per SNP and per individual (> 95%; >99% for SNPs with MAF<5%), Hardy-Weinberg Equilibrium (HWE p > 1 × 10−6), sex, and heterozygosity. In addition, to check whether any individuals were unexpectedly related to each other, a multidimensional scaling plot (using a pairwise-IBS matrix) with only one member of each known family was created. After the pedigree was checked for accuracy, the basic filters (MAF, genotyping success, HWE) were reapplied to the data. The GABRA2 SNP rs279871 was not initially genotyped on this array, and was imputed using ShapeIT (Delaneau, Marchini, & Zagury, 2012) in pre-phasing and IMPUTE2 (Howie, Donnelly, & Marchini, 2009) for genotype imputation. The posterior probability threshold for “best-guess” imputed genotype was 0.9. Genotypic information for this SNP was available for 100% of the
