Classification issues in catatonia.

Kahlbaum described catatonia as a disorder in which mood syndromes were the primary features and the characteristic symptoms were the motor signs. In the present study, we examined the relationship between motor features and other syndromes of psychosis, the clinical validity of Kahlbaum's concept of catatonia, its relationship to schizophrenia and mood disorder, and its nosological position in relation to DSM-III-R, DSM-IV and Leonhard's classification of endogenous psychoses. Patients with Kahlbaum's catatonia differed from patients with schizophrenia or mood disorder in various demographic and clinical variables. Positive and negative motor syndromes, although interrelated, showed a different correlational pattern with other psychotic syndromes. Catatonia did not appear to fit into any particular nosological category, although this issue largely depends on whether schizophrenia and mood disorders are broadly or restrictively defined. When definitions are more restrictive as in Leonhard's system, catatonia seems to be better accommodated as a "third psychosis", i.e. described by the concept of cycloid psychosis.