Twin concordance for DSM-III schizophrenia. Scrutinizing the validity of the definition.
DSM-III diagnoses were applied to 26 monozygotic (MZ) and 34 dizygotic (DZ) probands and their co-twins from the Maudsley Hospital (1948 to 1965) schizophrenic series of Gottesman and Shields. DSM-III criteria for schizophrenia were found to be highly reliable and valid, and to have a broad heritability of 0.85, which is comparable with the Research Diagnostic Criteria and Feighner criteria from which they were derived. When the full range of DSM-III diagnoses were considered, both affective disorder and schizophrenia were found in genetically identical individuals. The effect of DSM-III nosology on the twin series was also explored by adding other diagnoses to that of schizophrenia and observing the effect on the MZ/DZ concordance ratio. The addition of affective disorder with mood-incongruent delusions to the schizophrenia spectrum produced the largest increase in the ratio and, by implication, a "more genetic" combination than schizophrenia alone. The maximum MZ/DZ concordance ratio (7.68) was produced by schizophrenia, plus affective disorder with mood-incongruent delusions, plus schizotypal personality disorder, plus atypical psychosis. The effect of adding paranoid disorder (paranoia) and all other affective categories was a reduction in the ratio.
D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D004200:Diseases in Twins; D005260:Female; D006801:Humans; D008297:Male; D008370:Manuals as Topic / Q000592:standards*; D008875:Middle Aged; D019964:Mood Disorders / Q000145:classification / Q000175:diagnosis / Q000235:genetics; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000145:classification / Q000175:diagnosis / Q000235:genetics; D012559:Schizophrenia / Q000145:classification / Q000175:diagnosis* / Q000235:genetics; D012565:Schizophrenic Psychology; D012569:Schizotypal Personality Disorder / Q000145:classification / Q000175:diagnosis / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic