Epidemiology of schizophrenia. The disease model of schizophrenia in the light of current epidemiological knowledge

Abstract

Attempting an update of the epidemiology of schizophrenia, it is pointed out that schizophrenia seems to occur with the same core symptoms and almost at the same frequency in all countries and cultures studied. Methodologically sound studies have failed to produce evidence for a secular trend of the morbid risk. The genotype of schizophrenia is expressed as psychosis, personality disorders and non-specific disorders or it goes without manifest psychopathology. Minor brain anomalies are present in most cases. The British Child Development Study showed that behavioural, cognitive, emotional and neuromotor antecedents occur in 50% of cases, thus pointing to disordered brain development, very likely not specific to schizophrenia, since found in many other mental disorders as well. A look into the hidden early course of schizophrenia revealed a significant sex difference in age of onset and a prodromal phase of some 3 to 4 years throughout the cases. A case-control study showed that it is mainly during this early course before first admission that social disadvantage in schizophrenia arises. In the prephase a disease-related lack of social ascent plays a greater role than steps of social decline. The early social course differs between the sexes mainly due to an earlier onset of the disorder in males. The actual disease variables, that is, core symptoms and type of course, do not show any essential differences between males and females. These results indicate that schizophrenia is one of the rare uniform patterns of response of the brain, capable of being triggered by a large number of causes or favoured by non-specific risk factors. In this context the protective effect of estrogens will be discussed.