Psychological deficit from excessive alcohol consumption: evidence from a co-twin control study.

Twenty-five pairs of monozygotic twins discordant for either the alcohol dependence syndrome or heavy drinking were studied to determine the adverse cognitive effects of alcohol. The twins and their co-twins were well-matched for premorbid history and personality but twins with high alcohol consumption performed significantly less well overall on cognitive testing than their co-twins. Impaired performance in parts of the following tests was found: visual spatial ability, visual spatial recognition, Mill Hill vocabulary, Bexley Maudsley category sorting, tactual performance. The number of years of problem drinking correlated with inferior scores on subtests of the tactual performance test. This study provides further evidence that alcohol abuse produces long-term cognitive sequelae which may not be grossly evident in clinical practice, and which may occur even at relatively low levels of intake.