**1. Introduction**

194 Neuroscience – Dealing with Frontiers

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Extensive research over several decades indicates a strong relationship between alcohol use disorders and anxiety. Stress and anxiety are implicated in both the initiation of alcohol consumption and the maintenance of heavy drinking (Kushner et al., 1990; Pohorecky, 1981). For instance, anxiety disorders reliably precede the onset of alcoholism (Hettema et al., 2003) and over 35% of patients diagnosed with generalized anxiety disorder have engaged in self-medication with alcohol, defined as "drinking more than usual" in response to a stressor (Bolton et al., 2006). Stressors have also been linked to relapse in abstinent adults (Adinoff et al., 2005; Brown et al., 1995). Moreover, there is strong support suggesting that stress and alcohol abuse co-present so frequently as a result of common genetic factors in stress response systems. Genetically inherited variations in the hypothalamic-pituitaryadrenal (HPA) axis have been implicated in vulnerability to initial alcohol abuse, sustained alcohol addiction, and relapse (Crabbe et al., 2006; Kreek & Koob, 1998; Shaham et al., 2003). This paper will discuss the putative contribution of b-endorphin to the negatively reinforcing effects of alcohol.
