The power to detect cultural transmission in the Nuclear Twin Family design with and without polygenic risk scores and in the Transmitted-Non-transmitted (alleles) design

The aim of our study is to compare the power of two different approaches to detect passive genotype-environment covariance originating from simultaneous cultural and genetic transmission. In the traditional Nuclear Twin Family Design cultural transmission is estimated on the basis of the phenotypic covariance matrices of the mono- and dizygotic twins and their parents, where phenotyping is required in all family members. A more recent method is the Transmitted-Nontransmitted allele design, which exploits measured genetic variants in parents and offspring to test for effects of nontransmitted alleles from parents. This design requires genome-wide data and a powerful GWA (genome-wide association) study for the phenotype in addition to phenotyping in offspring. We compared the power of both designs. Using exact data simulation, we demonstrate that compared to the Transmitted-Nontransmitted design, the Nuclear Twin Family Design is relatively well-powered to detect cultural transmission and genotype-environment covariance. The power of the Transmitted-Nontransmitted design depends on the predictive power of polygenic risk scores. Adding polygenic risk scores of realistic effect size to the Nuclear Twin Family Design did not result in an appreciable increase the power to detect cultural transmission.