Interactive Effects of in Utero Nutrition and Genetic Inheritance on Cognition: New Evidence Using Sibling Comparisons

Justin Cook, Yale University
Jason Fletcher, Yale University

In this paper, we extend the gene-environment interaction framework approach by using sibling comparisons from the Wisconsin Longitudinal Study. In particular, we examine the potential interactive effects between early favorable nutrition status, as measured by birth weight, and variation in the FADS2 genotype in predicting young adult IQ. The main preliminary finding is that, while our baseline replication attempts are successful—we find similar results as the previous literature that genotype moderates the impact of early nutrition on later IQ—employing sibling comparisons shows the results and framework to be fragile to omitted family-level variables. The example has wider implications for the practice of investigating gene-environment interactions when the environmental exposure is not exogenous, and robust measures of the genome are not controlled in the analysis.