The diagnostic criteria and structure of catatonia

The classification of catatonia has fluctuated and underwent recent changes in DSM-5. The current study examines the prevalence of catatonia signs, estimates the utility of diagnostic features, identifies core catatonia signs, and explores their underlying structure.

We screened 339 acutely ill medical and psychiatric patients with the Bush Francis Catatonia Rating Scale (BFCRS). We examined prevalence and severity of catatonia signs and compared BFCRS, DSM-IV and DSM-5 diagnoses. We used principal component analysis (PCA) to examine the factorial validity of catatonia and item response theory (IRT) to estimate each sign's utility and reliability.

Out of the 339 patients, 300 were diagnosed with catatonia using the BFCRS and 232 catatonia diagnoses were validated by the treating provider based on selection for treatment with benzodiazepines or electroconvulsive therapy. Of the 232 validated catatonia cases, 211 (91%) met DSM-IV criteria but only 170 (73%) met DSM-5 criteria for catatonia. Staring was the most prevalent catatonia sign. PCA identified three components, interpretable as "Increased, Abnormal and Decreased Psychomotor Activity," although 63% of the variance was unexplained. IRT showed that Excitement, Waxy Flexibility and Immobility/Stupor were the best indicators of each factor. The BFCRS had many redundant items and as a whole had low reliability at low severity of catatonia, but good reliability at moderate-high severity of catatonia.

The structure of catatonia remains to be discovered.