Enhancing the Gene-Environment Interaction Framework: Evidence from Differential Responses to September 11th

Jason Fletcher, Yale University

This paper examines differential responses to the emotional stress from the 9/11 attacks on reports of depressive symptoms based on genetic variation—a gene-environmental interaction (GxE). This paper enhances the traditional GxE framework by incorporating a regression discontinuity design that leverages the coincidental survey window of Wave III of Add Health as well as the use of an environmental exposure (9/11) that is free of issues of gene-environment correlation. Several results emerge. First, as shown in previous work, individuals interviewed shortly after 9/11 report much higher levels of sadness and other depressive symptoms. The results from the GxE analysis suggest important interactive effects with the DRD4 gene. Individuals with the longer repeat version of DRD4 (which is correlated with excitability) show enhanced response to the stressor. Overall, this evidence suggests that genetic endowments are an important source of variation in response to a stressful event in producing poor mental health.