Has Kahlbaum syndrome disappeared or is it underdiagnosed? Reexamining the nosology of catatonia.

In contemporary psychiatric classification such as the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, and International Classification of Diseases, 10th Revision, catatonia is classified as a subtype of schizophrenia and not as an independent disorder. However, catatonia does not seem to obey nosological boundaries and is seen with both affective and nonaffective psychoses. We conducted a chart review of patients to examine the nosological status of catatonia. Our data suggest that catatonia is a syndrome of varied manifestation possibly related to both affective and nonaffective psychoses with a subgroup independent of both. Further prospective studies examining the natural course are needed, which could have significant implications on future classificatory systems.