Fig 3. The effect of correlation r_g between the direct and indirect effect sizes on the R² of PGS regression analyses from different study designs.

y-axis shows the ratio of R² from between family design (red) or sibling difference design (blue) vs. the proportion of phenotypic variance due to the direct effect in the population. The yellow box shows the ratio of R² from the sibling difference design based on PGS_mix vs. that in a sibling difference design based on PGS_dir. Each boxplot shows the simulation results of 200 repeats. In this figure, the variance of direct effect size and the variance of the environmental effect size were fixed at 1 and 3, respectively. The correlation between two sibling’s environments was fixed at 0.5. The two panels correspond to the results when the variance of the indirect effect size is 0.5 and 1, respectively.