Meta-analysis of GWA results across the 29 discovery cohorts did not yield genome-wide significant SNPs associated with extraversion. The lowest P-value observed was 2.9 × 10−7 for a SNP located on chromosome 2. There were 74 SNPs with P-values <1 × 10−5. The Manhattan and quantile–quantile plots are provided in Figs. 1 and 2. A list with the top five SNPs is given in Table 2. A list with all SNPs that reached the level of suggestive genome-wide significance (P < 1 × 10−5) is found in Supplementary Table 3. The results of all SNPs can be downloaded from www.tweelingenregister.org/GPC. A gene-based test showed one significant hit for LOC101928162, a long non-coding RNA site, P = 2.87 × 10−6. A list with the top five genes from the gene-based analysis is provided in Table 3. Supplementary Table 4 provides the top 30 genes. Among the top 30 genes was Brain-Derived Neurotrophic Factor (BDNF, P = 0.0003), a gene also implicated, though not genome-wide significant, in Terracciano et al. (2010), as was the BDNF anti-sense RNA gene (P = 0.0001).Table 2Top
