Because of differences in their behavioral and physiologic responses to stress, the types of stress-related pathology to which bold, proactive individuals and harm-avoidant, reactive individuals are vulnerable are distinct. Whereas the latter are at risk for internalizing disorders, such as depression and anxiety, the former are more likely to develop externalizing conditions, primarily characterized by impaired impulse control 10. In humans, anxiety is a risk factor for developing alcohol problems, and stress exposures can lead to craving and relapse 14, 15 55. It is also known that impulsivity or behavioral dyscontrol can predispose individuals to early and uncontrolled alcohol intake 14, 15. We find that carriers of the -2232 G allele exhibit higher levels of alcohol consumption when tested in the social group, a model for high-risk, impulsivity-related alcohol consumption. They also exhibit lower levels of the serotonin metabolite, 5-HIAA (data not shown), a neurochemical endophenotype observed both in macaques exposed to early life stress and among individuals with early-onset, Type II alcoholism 37, 56. It may be that, in humans, genetic variation that altered CRH system function could influence
