Dissecting the catatonia phenotype in psychotic and mood disorders on the basis of familial-genetic factors

Abstract

BackgroundThis study examines the familial aggregation (familiality) of different phenotypic definitions of catatonia in a sample of multiplex families with psychotic and mood disorders. MethodsParticipants were probands with a lifetime diagnosis of a DSM-IV functional psychotic disorder, their parents and at least one first-degree relative with a psychotic disorder. The study sample included 441 families comprising 2703 subjects, of whom 1094 were affected and 1609 unaffected. Familiality (h2) was estimated by linear mixed models using family membership as a random effect, with h2 indicating the portion of phenotypic variance accounted for by family membership. ResultsFamiliality estimates highly varied for individual catatonia signs (h2=0.17–0.65), principal component analysis-derived factors (h2=0.29–0.49), number of catatonia signs present (h2=0.03–0.43) and severity of the catatonia syndrome (h2=0.25–0.59). Phenotypes maximizing familiality estimates included individual signs (mutism and rigidity, both h2=0.65), presence of ≥5 catatonia signs (h2=0.43), a classical catatonia factor (h2=0.49), a DSM-IV catatonia syndrome at a severity level of moderate or higher (h2=0.59) and the diagnostic construct of psychosis with prominent catatonia features (h2=0.56). Familiality estimates of a DSM-IV catatonia syndrome did not significantly differ across the diagnostic categories of psychotic and mood disorders (h2=0.40–0.47). ConclusionsThe way in which catatonia is defined has a strong impact on familiality estimates with some catatonia phenotypes exhibiting substantial familial aggregation, which may inform about the most adequate phenotypes for molecular studies. From a familial-genetic perspective, the catatonia phenotype in psychotic and mood disorders has a transdiagnostic character.