This example is a textbook case of interaction. In the end, VanderWeele’s analysis proves three important things about the smoking gene. First, it does not significantly increase cigarette consumption. Second, it does not cause lung cancer through a smoking-independent path. Third, for those people who do smoke, it significantly increases the risk of lung cancer. The interaction between the gene and the subject’s behavior is everything.
how is interaction captured by the causal graph!?!
