What do we really know about late-onset schizophrenia?

Actual knowledge on classical late-onset schizophrenia, i.e. the schizophrenic disorders with onset after age 40 years, is reviewed regarding incidence, symptomatology and course. As is shown, sound empirical knowledge is scarce. Reasons for this are, on the one hand, the conceptual and terminological confusion which has occurred internationally regarding this illness group, and, on the other hand, the methodological limitations of the empirical studies conducted on this clinical picture thus far. If we only draw on classical late-onset schizophrenia, as originally defined by Bleuler, and primarily on methodologically sound studies, as well as on own studies, we can nevertheless conclude that the term "late-onset schizophrenia" could be omitted. Late-onset schizophrenia does not seem to be a distinct entity, but instead seems to belong to the same illness group as classical schizophrenia with earlier onset. Slight differences in symptomatology and course are probably due to unspecific influences of age. The markedly higher proportion of women among late-onset cases, as well as our finding that symptomatology and course of late-onset women are comparably poor, could possibly be explained by an effect of the female sex hormone oestradiol.