MONOAMINE OXIDASES AND ALCOHOLISM .2. STUDIES IN ALCOHOLIC FAMILIES

Thirty-five alcoholic families have been studied to investigate the re lationship between DNA markers at the monoamine oxidase (MAO) loci and 1) platelet activity levels and 2) alcoholism. A quantitative linkage analysis failed to reveal any evidence that the variation in activity levels cosegregates with the DNA markers. A sib-pair analysis did not reveal a significant excess of MAO haplotype sharing among alcoholic sibs, although the deviation from random sharing was in the direction consistent with an X-linked component. A reanalysis of platelet MAO ac tivity levels in a subset of these families revealed that the lower le vels previously found in alcoholics is more likely due to the differen ces between males and females. Only among males and only when a ''broa d'' definition of alcoholism is used (and MAO activity levels are tran sformed to normality) does it appear that alcoholics have depressed ac tivities compared to nonalcoholics. Finally, when the confounding due to gender difference is removed, no differences between type I and typ e II alcoholics are found in these families. (C) 1995 Wiley-Liss, Inc.