Quantitative trait analyses were performed for these temperaments using linear regression in PLINK.33 The trait distribution for each temperament was approximately normal in this sample. Three covariates were incorporated into the model as determined appropriate via correlation analyses: gender, Global Assessment of Functioning score, and age at onset of BD. Genomic inflation factors for the analysis of each subscale ranged from 1.00 to 1.01, so no correction for population stratification was deemed necessary. This is consistent with the negligible population structure that has generally been observed in the complete GAIN and TGEN samples, as described elsewhere (32). For comparison purposes, analysis of BD in the 1,566 Wave 5 subjects and combined 1,434 GAIN and TGEN controls was performed using logistic regression in PLINK.
