Background: Cycloid psychosis is a psychiatric disorder known for about 100 years. This disorder is at present partly and simplified represented in the ICD-10. Sampling and Methods: Over a period of 15 months, 139 consecutively acutely admitted psychotic patients were assessed, by means of different diagnostic instruments, in order to investigate the prevalence and the symptom profile of cycloid psychoses. In addition, the concordance between the diagnoses cycloid psychosis, brief psychotic disorder, and acute polymorphic psychotic disorder with or without symptoms of schizophrenia was calculated. Results: Cycloid psychoses were present in 13% of the patients. There was a significant but small overlap with the DSM brief psychotic disorder and the ICD acute polymorphic psychotic disorder. Conclusions: This study demonstrates that cycloid psychoses can be identified with the proper diagnostic instruments in a proportion that is also found in other studies. Since this type of psychosis entails a distinct prognosis and may require a specific treatment, its identification is of clinical importance. Limitations are the nature of the psychiatric facility with an inherent bias in the selection of patients and the lack of a long-term evaluation. Copyright

Acute polymorphic psychotic disorder, Cycloid psychosis, Diagnosis, cycloid psychosis, Nonschizophrenic psychosis,
Department of Psychiatry

van der Heijden, F.M.M.A, Tuinier, S, Kahn, R.S, & Verhoeven, W.M.A. (2004). Nonschizophrenic psychotic disorders: The case of cycloid psychoses. Psychopathology, 37(4), 161–167. doi:10.1159/000079419