Hitherto, nearly all treatments in the literature as well as our models have assumed that EPs ought to reflect genetic risk factors for PD. In fact, it has been seen as a problem that EPs might reflect environmental etiological factors. However, just as EPs might help researchers index genetic risk factors, the same logic can be applied to environmental risk factors. That is, a researcher might be interested in finding EPs that provide more useful indexes of environmental factors. An example would be finding a neuroanatomic consequence of the teratogenic effects of maternal substance use, which in turn affects adolescent antisocial behavior. This EP could prove useful in identifying specific substances that have more distal effects on the antisocial behavior outcome. All the points made above to ‘genetic EPs’ would apply equally to such ‘environmental EPs.’ For example, EP might index only the liability or it might mediate the pathway from the environmental trauma to the disorder.
