The age of onset of schizophrenia and the theory of anticipation

The clinical phenomenon called anticipation is usually defined as a decreas e in age at onset and/or an increase in disease severity in successive gene rations of afflicted families. The purpose of this study was to examine var iables that might influence anticipation in schizophrenia. A total of 380 A ustrian patients, born between 1935 and 1964, met criteria for schizophreni a with ICD-8 or ICD-9, SADS-L and DSM-III-R criteria. The inclusion criteri a also required medical records of patients to contain information about th e year of birth, season of birth, age at onset, accidents or meningoencepha litic diseases during childhood, first- and second-degree relatives afflict ed with schizophrenia, sibship size, sib order, education of patient, age o f parents, occupation of parents, loss of parents, and place of residence. A Cox multiple-regression analysis showed three factors as having a signifi cant influence on the age of disease onset, including year of birth (which had the largest influence), family history (sporadic cases showed an onset 2 years later than familial cases) and residence (urban dwellers showed psy chotic symptoms approximately 1 year sooner than rural ones). A Kaplan-Meie r Survival Analysis showed that younger cohorts had onset approximately 10 years earlier in sporadic and familial cases. This cohort effect might be a major source of bias in studies of anticipation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.