Neuroticism data (n=6 032) were drawn from three Australian cohorts of twin families measured in 1980, 1989 and 2002 on the EPQ 23- (1980 cohort) or 12-item scale (1989 and 2002 cohorts) at a mean age of 32.5±11.8 years (62.9% female). Extraversion data (n=5 443) were available from the 1980 and 1989 cohorts, based on respective 21- and 12-items of the EPQ; the mean age was 31.6±12 years (64.7% female). For details on cohort ascertainment and measure reliability see Birley et al. (2006). Participants were genotyped on an Illumina SNP microarray chip (317K, 370K-array, 370-Quad, 610-Quad, or humanCNV370-Quadv3) in different genotyping centres with imputation to ~2.5 million SNPs using Hap Map Phase II data and MACH. QC procedures were applied separately to each project (Wray et al. 2010). Association analysis included sex, age, cohort, and the population stratification components as covariates; a variance components approach accounted for relatedness among individuals in MERLIN (Chen and Abecasis 2007).
