To further assess pleiotropic SNP effects, prediction analyses were performed in which polygenic scores for extraversion and neuroticism were used to predict phenotypic variation in mood measures. Because anxiety, depression and psychological distress symptoms were available in a subset of cohorts, polygenic scores for personality were estimated from GWAS meta-analysis results based on cohorts who did not have the mood measure under investigation. Thus, the prediction cohort was independent of the cohort in which polygenic scores were based. Polygenic scores were calculated (in PLINK; Purcell et al. 2007) by summing across all genotyped SNPs, where the number of reference alleles (0, 1 or 2) at that SNP was multiplied by the effect size of that SNP. Each of the personality polygenic scores was correlated with each of the mood traits, controlling also for the number of SNPs used in the scoring. This was done separately for each cohort; a meta-analysis of the correlations was conducted in META 5.3 (Schwarzer 1989). For the replication cohorts, personality polygenic scores were estimated from all the Discovery cohorts, with personality predicted in the Australian cohort and mood states predicted in the German and NTR cohorts.
