The Kahlbaum syndrome: a study of its clinical validity, nosological status, and relationship with schizophrenia and mood disorder.

Kahlbaum described catatonia as a disorder in which mood syndromes were the primary features and characteristic symptoms were the motor ones. However, after Kahlbaum this concept has not been taken into account and catatonia has been identified with motor features alone. In the present study, we assessed the clinical validity of Kahlbaum's concept of catatonia, its nosological position in relation to DSM-III-R, DSM-IV, and Leonhard's diagnostic criteria, and its relationships with schizophrenia and mood disorder. Of 567 patients consecutively admitted due to a functional psychotic disorder, 45 met criteria for catatonia according to Kahlbaum's concept (the Kahlbaum syndrome [KS]). Patients with the KS were differentiated from those with schizophrenia and mood disorders across a number of demographic and clinical variables, the differences being greater with the former than with the latter group. KS does not appear to fit any particular nosologic category, although this issue largely depends on whether schizophrenia and mood disorder are broadly or restrictively defined. When definitions of both disorders are most restrictive, as in the case of the Leonhard system, KS seems better accommodated as a "third psychosis". Overall, the data raise the possibility that KS is either a variant of mood disorder, or a distinct clinical entity.