The five genes containing the strongest SNP hits of association with the Persistent Externalizing factor (8 hits with p < 0.001) were GRID2, GABBR2, CSMD1, LINGO2, and MARCH1. No individual SNP remained significant after correcting for multiple comparisons, and enrichment effects pertain to the set of SNPs as a whole rather than any particular SNP. Nevertheless, it is worth noting how polymorphisms in these 5 genes performed in Aliev et al.’s (2015) previous study this gene set and individual externalizing phenotypes. They found no significant associations between any phenotype and LINGO2, and one association between MARCH1 and extraverted personality. Furthermore, CSMD1 had significant hits for sensation seeking, and GRID2 (which encodes a glutamate receptor subunit) had hits with respect to both conduct disorder symptoms and sensation seeking. Lastly, among these five genes, GABRR2 (which encodes a GABA receptor subunit) showed the most hits in the COGA sample, with hits for antisocial personality symptoms, conduct disorder symptoms, extraversion and sensation seeking. Thus, across both studies, GABRR2 was the one of the most promising genetic signals to emerge.
