Genome-wide association meta-analyses were carried out as described in de Moor et al.25 without inclusion of the GAIN-MDD data. Meta-analyses were based on GWA analyses for the five personality traits conducted in each study with linear regression (under an additive model) and included sex and age as covariates. Meta-analyses of the results were conducted by the weighted inverse variance method as implemented in METAL (http://www.sph.umich.edu/csg/a becasis/metal/index.html),53 which computes a pooled effect estimate (ln(beta)), its s.e. and its P-value by weighing the effect estimates of individual samples by the inverse of its variance and by taking into account the direction of effect.
