Epidemiology of schizophrenia: a European perspective.

Since its inception, the concept of dementia praecox and, later, of schizophrenia has been one of the most disputed entities in modern medicine. Schizophrenia was, and still is, defined by its clinical symptoms and their characteristic evolution over time. No external validating criteria for the diagnosis have been established, in spite of a host of suggestive biological findings, among which the genetic data carry most weight. This absence of clear-cut substrate markers and indicators underscores the importance of the epidemiological perspective in the study of the disorder. The European contributions to the epidemiological description and understanding of schizophrenic morbidity are numerous. They range from community surveys and studies of pedigrees to case-control designs for assessment of risk factors and long-term followup investigations of course and outcome. This review focuses on epidemiological approaches to schizophrenia that have attempted to highlight the essential attributes of a disease: its incidence and prevalence, ecology, and associated features. It is difficult to generalize about European epidemiological research in schizophrenia, because of the coexistence of a variety of "schools," traditions, and approaches. It is nevertheless possible to discern several clear trends in European epidemiological investigations of schizophrenia that can, to some extent, be contrasted to North American developments.