[Schizophrenia and delusions in middle aged and elderly patients. Epidemiology and etiological hypothesis].

Knowledge of the similarities and differences between early- and late-onset schizophrenia and between late-onset schizophrenia and paranoid disorder of old age and very old age is fragmentary. We compared diagnosis, subtypes, syndromes and symptoms between first-episode schizophrenia (ICD-9: 295) and paranoid disorder (ICD-9: 297, 298.3/4.) over the life cycle in a population-based (N = 232) and a clinical first-admission sample (N = 1109). Apart from different age patterns of the sexes only two symptom groups were significantly different between early- and late-onset illness: paranoid and systematic delusions showed a linear increase, symptoms of disorganisation a linear decrease over the life cycle. Clearly different between early- and late-onset illness were the neurobiological and psychological risk factors, suggesting that both neurodevelopmental and neurodegenerative disorder causes psychopathology typical of schizophrenia. Late- (40 to 60) and very-late-onset (over 60) cases of both groups of illness showed the same symptom profiles, merely the number of symptoms being higher in the group diagnosed with schizophrenia. Age was the only factor significantly contributing to a clinico-diagnostic differentiation of schizophrenia from paranoid disorder beyond age 40.