Alcohol use disorders (AUDs) are regarded as one of the most severe public health problems worldwide, being the leading cause of a wide variety of morbidity and mortality conditions in many developed countries. Research has amply demonstrated that both genetic and environmental factors contribute to the development of these disorders [1]–[5]. The psychoactive effects of alcohol are mediated through its influence on different functional systems in the brain, including the dopamine, serotonin, gamma-aminobutyric acid, glutamate, and opioid peptide systems. Another system whose involvement in the etiology and continuation of alcohol abuse has recently been proposed is the circadian clock mechanism [6]. The circadian clock optimizes the adaptation of an organism to its internal and external environment. In animal models, the time of day was demonstrated to shape the rewarding effect of substance use [7], [8]. In turn, circadian rhythmicity was found to be influenced by substance use, in general, and alcohol use, in particular, notably heavy use [9]. This becomes apparent in severe disorganizations of physiological clock systems, such as sleep, body temperature or blood pressure during chronic alcohol abuse, dependence and withdrawal, with these disorganizations being based on altered expression of the clock genes.
