A review of the literature on the cognitive effects of alcohol hangover.

AIMS: Alcohol misuse is a prime social and health problem in the UK. This paper presents a critical review of literature on the performance effects in the morning after binge drinking - during the alcohol hangover. Several pathophysiological changes that both follow and outlast acute intoxication may give rise to alcohol hangover effects. We have identified 27 English language peer-reviewed studies that investigate aspects of psychological performance during alcohol hangover following controlled alcohol ingestion. However, the majority of studies had basic methodological shortcomings. Of eight laboratory studies rigorous enough to warrant serious attention, only two showed effects. We interpret these largely negative findings as evidence of an insensitivity that is intrinsic to laboratory-based studies of performance under the influence of alcohol. Several studies have investigated the cognitive consequences of hangover subsequent to naturalistic consumption, where participants have chosen what and where to drink. Although these studies have tended to show effects, participants were always informed at the outset that hangover effects were to be assessed, and participants knew which was the hangover condition. Under these circumstances expectancy effects have possibly contaminated the results significantly. Therefore, naturalistic alcohol consumption studies (and laboratory studies that did not employ a placebo) can be considered as being suggestive of hangover effects, but should not be interpreted as providing definitive evidence of such effects. In conclusion, although there is empirical evidence showing impaired performance as a result of the alcohol hangover, future studies should confirm these findings and overcome the shortcomings of previous research.