Objective: The authors assess the present position of catatonia in diagnostic classification systems and consider the merits of designating catatonia as a separate diagnostic category with defined criteria.
Method: Following the logical steps to establish diagnostic validity when the etiology of a syndrome is unknown, the authors review the literature on the features that delineate catatonia as a syndrome, the prevalence and response to treatment of catatonia, and the conditions that are associated with catatonia.
Results: Catatonia is a well-defined syndrome that can be reliably ascertained. Although more than 40 motor signs of catatonia are known, the presence of two prominent features for 24 hours or longer is sufficient to identify the syndrome. Catatonia is found in about 10% of acutely ill psychiatric inpatients and is more commonly observed in persons with mood disorder than in those with schizophrenia. It is found in many conditions and presents mainly as retarded-stuporous or excited-delirious forms. Catatonia responds to specific treatments, including sedative anticonvulsants (barbiturates and benzodiazepines) and ECT.
Conclusions: Catatonia can be distinguished from other behavioral syndromes by a recognizable cluster of clinical features. Catatonia is sufficiently common to warrant classification as an independent syndrome. It can be reliably identified, has a typical course when appropriately treated, responds to specific treatments, and is worsened by other treatments. It is associated with many pathophysiologic processes and most often with mood disorder. These findings, which are consistent with established methods of defining distinct diagnostic groupings, support consideration of catatonia as an individual category in psychiatric diagnostic systems.