“Genomic Analysis of Family Data Reveals Additional Genetic Effects on Intelligence and Personality”, 2017-02-06 (; backlinks; similar):
Pedigree-based analyses of intelligence have reported that genetic differences account for 50–80% of the phenotypic variation. For personality traits, these effects are smaller with 34–48% of the variance being explained by genetic differences. However, molecular genetic studies using unrelated individuals typically report a heritability estimate of around 30% for intelligence and 0%–15% for personality variables. Pedigree-based estimates and molecular genetic estimates may differ because current genotyping platforms are poor at tagging causal variants, variants with low minor allele frequency, copy number variants, and structural variants.
Using ~20,000 individuals in the Generation Scotland family cohort genotyped for ~520,000 single-nucleotide polymorphisms (SNPs), we exploit the high levels of linkage disequilibrium (LD) found in members of the same family to quantify the total effect of genetic variants that are not tagged in GWASs of unrelated individuals. In our models, genetic variants in low LD with genotyped SNPs explain over half of the genetic variance in intelligence, education, and neuroticism.
By capturing these additional genetic effects, our models closely approximate the heritability estimates from twin studies for intelligence and education, but not for neuroticism and extraversion.
From an evolutionary genetic perspective, a substantial contribution of genetic variants that are not common within the population to individual differences in intelligence, education, and neuroticism is consistent with mutation-selection balance.
…For Neuroticism, the final model consisted of contributions from the variance components G and K. Additive common genetic effects explained 11% (SE = 2%) of the variance with pedigree-associated variants explaining an additional 19% (SE = 3%). Whereas none of the environmental components were statistically-significant, the family component accounted for 2% of the variance in the full model and 1% in a model that included only the G and the K in addition to F.
For Extraversion, the only detectable source of genetic variation came from the G, which accounted for 13% (SE = 2%), with F explaining a further 9% (SE = 1%) of the phenotypic variation. The lack of pedigree-associated genetic effects could be due to low statistical power, as K explained 5% of the variance in the full model and 6% in a GKF model, but with a relatively large SE, estimated at 5%.