Subdividing the functional psychoses: a family hereditary approach

Abstract

SYNOPSIS Family genetic data, based on standardized and independent diagnostic procedures of index and secondary cases, confirmed the dichotomy between schizophrenias and aifective disorders. The classical schizophrenic subtypes exhibited a significant tendency towards homotypia among their secondary cases. The genetic evidence did not support the monopolar-bipolar subdivision of affective disorder. Schizo-affective disorders impinged on the clear-cut schizophrenic and affective psychotic disorders and there was no homotypical tendency among the relatives of index cases with this diagnosis. THE GENETIC ARGUMENT AND METHODOLOGICAL REQUIREMENTSThe diagnostic categorization of the major psychoses depends on social criteria -psychopathology, course and outcome, assumed causation, trigger-mechanism (Ausloser) and family hereditary data. Family genetics are concerned with the prevalence of homotypical (i.e. analogical or similar psychopathological characteristics), as against heterotypical secondary cases among the consanguineous relations. Homotypia is traditionally interpreted by geneticists as an indicator of a genetic entity; if absent, then phenocopia is inferred.From the genetic standpoint, the dichotomy of functional psychoses into a group of schizophrenias (ICD 295) and affective disorders (ICD 296) is based on an increased incidence of the respective psychoses among first-degree relatives: there are about 10 % homotypical disorders, but no increased frequency of heterotypical psychoses. The genetic interpretation of these findings is by far the most convincing. The same argument may also be applied to the question of whether a clinical subdivision of the major functional psychoses may be supported by family hereditary data, i.e. the finding of homotypia in the subgroups. With regard to the classical subdivision of the schizophrenias into schizophrenia simplex (ICD 2950), hebe-

Genetic Epidemiology of Major Depression: Review and Meta-Analysis

“…If relative or co-twin diagnoses are assigned without "blindfolding," it is impossible to know the degree to which the results are contaminated by experimental bias. For archival purposes, we provide the citations for the family (23)(24)(25)(26)(27)(28)(29)(30) and twin studies (31)(32)(33)(34) that were not included.…”