Several issues are relevant in reconciling the present study results with existing theory. First, retrospective patient reports suggesting the need for more alcohol to get the same effects as compared to when one first started drinking regularly is not sufficient support for chronic tolerance. The well-controlled present study findings are not consistent with robust chronic tolerance to alcohol’s subjective effects suggesting that some of the users’ reports of lessened effects may be influenced by other factors. Second, studies of chronic exposure to alcohol derived from animal models of addiction, while providing critical information about the behavioral and physiological correlates of consumption (51), are not able to shed light on changes in the euphoric effects of drinking in humans, and how these change over time. Third, some theories of addiction, such as allostasis, indicate development of a deficit in reward, or a change in aversive states and stress responses. Although our data do not provide support for this idea, it is possible this putative stage requires more than a decade to development or that it exists only in those prone to
