A possible biochemical vulnerability (trait) marker is examined in a cross-sectional study to determine the biochemical factors associated with the development of alcoholism in a population of non-adult children of alcoholics. The activity of adenylate cyclase, an enzyme that plays a role in the signal transduction pathway of several hormones and neurotransmitters, is assessed in blood platelets. This activity was reported to be lower in blood cells of alcoholics and abstinent alcoholics compared with that in controls. In addition, dysregulation of adenylate cyclase in the CNS of animals seems to be involved in drug-seeking behaviour. The relation between these biochemical findings and psychopathology is currently being investigated in a project by the Amsterdam Institute for Addiction Research.