PRENATAL FACTORS IN THE PATHOGENESIS OF SCHIZOPHRENIA

The excess of winter-spring births among individuals suffering from sc hizophrenia provides strong evidence for the existence of some prenata lly occurring factors in the pathogenesis of schizophrenia. Recent epi demiological findings suggest that maternal viral infections during th e second trimester of pregnancymay play a crucial role in the aetiolog y of adult schizophrenia. A 'two-hit window' hypothesis of the mechani sm of action of prenatal factors in,the pathogenesis of schizophrenia suggests at least two time-specific prenatal aetiological events. The observed association between prenatal viral infection and increased in cidence of adult schizophrenia need not be a direct cytotoxic result o f the viral infection, but may be caused indirectly, for example from foetal minor cerebral haemorrhages produced by the anticoagulant effec ts of aspirin.