A controlled family study of late-onset non-affective psychosis (late paraphrenia)

Abstract

Background: The relationship between those schizophrenia-like conditions that have their onset in late life and early-onset schizophrenia is unclear. Very few family history studies of patients with late-onset psychosis have been reported, and it is not known whether their relatives have an increased risk of psychosis. Method: Information was collected on the psychiatric morbidity of 269 firstdegree relatives of patients with schizophrenia or delusional disorder with an onset after the age of 60 (late paraphrenia), and 272 first-degree relatives of healthy elderly control subjects, using a research diagnostic instrument. Results: With a narrow age range (15-50 years) at risk, the estimated lifetime risk of schizophrenia was 1.3% in the relatives of both cases and controls. With a wider age range (15-90 years) at risk, estimated lifetime risk of schizophrenia was 2.3% for the relatives of cases, and 2.2% for the relatives of controls. However, depression was significantly more common among the relatives of cases than controls. Conclusion: Those schizophrenia-like psychoses with onset in late life are not genetically associated with schizophrenia.