Heritability of Schneider's first-rank symptoms.

Abstract

Schneider's first-rank symptoms are given particular weight when making a diagnosis of schizophrenia, but the nuclear syndrome, characterised by one or more first-rank symptoms, has been found previously to have no heritability. To estimate the heritability of the nuclear syndrome. A total of 224 twin pairs (106 monozygotic, 118 same-gender dizygotic) were ascertained from the Maudsley Twin Register in London via probands with any psychosis. Lifetime-ever first-rank symptoms were rated using the OPCRIT checklist. Probandwise concordance rates were calculated for the nuclear syndrome and a heritability estimate was derived from biometric model fitting. Probandwise concordance rates were 13/49 (26.5%) for monozygotic and 0/45 to 2/46 (0.0-4.3%) for dizygotic pairs. The heritability estimate for the best-fitting model was 71% (95% CI 57-82). These results indicate that the nuclear syndrome shows substantial heritability, although this is slightly lower than that for schizophrenia as defined by the DSM and ICD systems.