Cognitive functioning in sober social drinkers: a review of the research since 1986.

Several studies published in the late 1970s and early 1980s reported that quantity of beverage alcohol typically ingested was inversely related to cognitive performance in sober social drinkers. After reviewing the widespread attempts to confirm these findings, Parsons concluded in 1986 that (1) there was no consistent evidence for residual impaired cognitive functions as a result of alcohol ingestion in sober social drinkers and (2) the importance of the problem called for continued research with improved methodology. In this article we evaluate the literature since 1986. Out of 19 pertinent studies, 17 investigated the relationships between cognitive tests and sober social drinking, one investigated event-related potentials (ERPs) and one investigated both cognitive performance and ERPs. Seven studies found that heavy social drinkers had significantly worse performance on one or more cognitive tests than the light drinkers. Ten studies reported negative results. Samples in negative studies had significantly lower averages of weekly drinks (mean = 16.4) than the samples in the positive studies (mean = 41.9). Both ERP studies found differences between heavy and light social drinkers. Our conclusions support an alcohol-causal-threshold hypothesis and suggest the following testable hypotheses: persons drinking five or six U.S. standard drinks per day over extended time periods manifest some cognitive inefficiencies; at seven to nine drinks per day, mild cognitive deficits are present; and at 10 or more drinks per day, moderate cognitive deficits equivalent to those found in diagnosed alcoholics are present.