Clinical and epidemiological observations have revealed that alcohol abuse and alcoholism are associated
with widespread disruptions in sleep and other circadian biological rhythms. As with other psychiatric
disorders, animal models have been very useful in efforts to better understand the cause and effect
relationships underlying the largely correlative human data. This review summarizes the experimental
findings indicating bidirectional interactions between alcohol (ethanol) consumption and the circadian
timing system, emphasizing behavioral studies conducted in the author’s laboratory. Together with
convergent evidence from multiple laboratories, the work summarized here establishes that ethanol
intake (or administration) alters fundamental properties of the underlying circadian pacemaker. In turn,
circadian disruption induced by either environmental or genetic manipulations can alter voluntary
ethanol intake. These reciprocal interactions may create a vicious cycle that contributes to the downward
spiral of alcohol and drug addiction. In the future, such studies may lead to the development of chronobiologically
based interventions to prevent relapse and effectively mitigate some of the societal
burden associated with such disorders.