title: The genetic heterogeneity of "schizophrenia".
abstract: The main reason for the inconsistent findings in schizophrenia research is the lack of diagnostic conformity. This has not changed markedly following the introduction of modern operational diagnostic systems. Taking schizophrenia as a disease entity or assuming schizophrenia spectrum psychoses to represent a continuum of diseases without any clear dividing lines, the results of family and twin studies point to a multifactorial etiology based on a polygenic mode of transmission. Further, then it has to be assumed a familial continuum from schizophrenia to affective psychosis and other spectrum disorders. However, in family and twin studies based on Leonhard's classification, there is clearcut evidence that schizophrenic spectrum psychoses have to be divided into clinical and etiological subgroups with a completely different genetic background. For example, systematic catatonia is, for the most part, a sporadic disease, whereas periodic catatonia aggregates in families in a manner consistent with a major gene effect. Further, the results indicate that schizophrenic spectrum psychoses consist of three main valid categories: cycloid psychoses, unsystematic schizophrenias and systematic schizophrenias. In the case of cycloid psychosis and systematic schizophrenias, genetic loading seem to be very low, while "environmental" factors, for example, birth complications, may play an important etiological role. Unsystematic schizophrenias, however, are predominantly inherited and "environmental" factors are not very prominent.
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Wurzburg, Fuchsleinstrasse 15 97080 Wurzburg, Germany. beckmann@mail.uni-wuerzburg.de
authors.forename: H
authors.initials: H
authors.lastname: Beckmann
authors.forename: E
authors.initials: E
authors.lastname: Franzek
mesh_terms: D000328:Adult; D000368:Aged; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D010507:Periodicity; D011618:Psychotic Disorders / Q000209:etiology; D012559:Schizophrenia / Q000175:diagnosis / Q000235:genetics*; D012560:Schizophrenia, Catatonic / Q000175:diagnosis / Q000235:genetics; D012565:Schizophrenic Psychology; D018433:Twin Studies as Topic; D014427:Twins / Q000235:genetics
chemical_list: D005819:Genetic Markers