Recent studies have estimated that a large proportion of heritability can be explained by common variation, based on identity-by-descent sharing of distantly related individuals (28). It has been shown that ∼3% of variance (corresponding to an AUC of 0.65) (23) in schizophrenia risk can be explained by a polygenic model, including a large number of loci that did not achieve genome-wide significance (29). Various attempts have been made to use highly polygenic risk scores based on these non-significant loci for prediction in different diseases, with varying degrees of success (30–32).
