The proportion of variance explained (R2) by the schizophrenia polygenic risk score was computed by comparing the regression model with the age, sex, and ten principal components to the regression model that includes the schizophrenia polygenic risk score variable in addition to age, sex and principal components. Because the analyses used logistic regression, the reported R2 is the difference between the Nagelkerke’s pseudo-R2 from the two models.
