Considered together, these studies provide substantial empirical evidence for a dichotomous typology of alcoholism, a key dimension of which is age of alcoholism onset. Further, the pathologic mood and behavioral dimensions that distinguish EOAs from LOAs may reflect abnormalities in serotonergic neurotransmission. These differences may help explain why later-onset/lower vulnerability alcoholics show different responses than earlier-onset/higher vulnerability alcoholics to treatment with serotonergic medications (see Kenna 2010 for a comprehensive review), including selective serotonin reuptake inhibitors (Kranzler et al. 1996, Pettinati et al. 2000, Chick et al. 2004) and the serotonin-3 receptor antagonist ondansetron (Johnson et al. 2000a, Kranzler et al. 2003).
