BACKGROUND For many common medical and neuropsychiatric disorders, early age at onset reflects high familial liability to illness. However, for schizophrenia, most studies do not find such a relationship.
METHOD Using Cox proportional hazard modes, we investigate this question in the epidemiologically-based Roscommon family study.
RESULTS No relationship was found between age at onset in schizophrenic probands and the hazard rate for schizophrenia in their relatives. Similar results were obtained when the definition of illness was expanded to include schizoaffective disorder and other non-affective psychoses.
CONCLUSIONS For schizophrenia, a 'common-sense' model for age of onset (i.e. those with highest familial liability to illness succumb first while those with lower liability survive longer before falling ill) does not seem to apply. Our results are more consistent with a model in which variation in age at onset of schizophrenia is due to random developmental effects or to environmental experiences unique to the individual.