If the variance for intelligence is primarily additive, then why are IQ GWAS heritability estimates significantly under the heritability estimates you see from twin studies (or even GWAS heritability for height)?
The SNP heritability estimates for IQ of (h^2 = ~0.2) are primarily based on a low quality test that has a test-retest reliability of 0.6, compared to ~0.9 for a gold-standard IQ test. So a simple calculation to adjust for this gets you a predicted SNP heritability of 0.2 * (0.9 / 0.6)^2 = 0.45 0.2 * (0.9 / 0.6) = 0.30 for a gold standard IQ test, which matches the SNP heritability of height. As for the rest of the missing heritability: variants with frequency less than 1% aren’t accounted for by the SNP heritability estimate, and they might contribute a decent bit if there are lots of them and their effects sizes are larger.
EDIT: the original adjustment for test-retest reliability was incorrect: the correlations shouldn’t be squared.
If the variance for intelligence is primarily additive, then why are IQ GWAS heritability estimates significantly under the heritability estimates you see from twin studies (or even GWAS heritability for height)?
The SNP heritability estimates for IQ of (h^2 = ~0.2) are primarily based on a low quality test that has a test-retest reliability of 0.6, compared to ~0.9 for a gold-standard IQ test. So a simple calculation to adjust for this gets you a predicted SNP heritability of
0.2 * (0.9 / 0.6)^2 = 0.450.2 * (0.9 / 0.6) = 0.30 for a gold standard IQ test, which matches the SNP heritability of height. As for the rest of the missing heritability: variants with frequency less than 1% aren’t accounted for by the SNP heritability estimate, and they might contribute a decent bit if there are lots of them and their effects sizes are larger.EDIT: the original adjustment for test-retest reliability was incorrect: the correlations shouldn’t be squared.