aThe maximum prevalence for KMZis 1, so λMZ= KMZ/K is constrained to be ≤1/K. λMZwas calculated from probandwise concordance rates KMZand prevalence rates if λMZwas not directly reported. bEstimated from either sibling, dizygotic twin or first degree relative risks. c broad sense heritability on the risk scale (Equation 1). dThis ratio is expected to be 1 in the absence of dominance effects on the risk scale. eThis ratio is expected to be 2 under an additive model on the risk scale. fThis ratio is expected to be 1 under the unconstrained Risch model. gCalculated from the estimates of K and λSib[41, 42], constrained to a maximum of 1.