Incidence and diagnostic stability of ICD-10 acute and transient psychotic disorders.

Objective: The 10th Revision of the International Classification of Diseases (ICD-10) introduced a new diagnostic category, F23 acute and transient psychotic disorders (ATPD) to embrace clinical concepts such as the French bouffée délirante, Kleist and Leonhard's cycloid psychoses, and the Scandinavian reactive and schizophreniform psychoses. The relative rarity of these disorders and insufficient follow-up studies with adequate numbers of patients makes ATPD classification as uncertain as their validity. The aim of this study was to evaluate incidence and validity of ATPD in terms of diagnostic stability.
Method: A 6-year analysis of readmission patterns of all subjects listed in the Danish psychiatric central register as having been first-ever admitted to hospital or treated in outpatient services with a diagnosis of ATPD from January 1 to December 31, 1996, was conducted.
Results: The incidence of ATPD was 9.6 per 100 000 population, with a higher rate of females than males (9.8 vs 9.4). Incidence rates by age group were higher for males than for females, with a marked reversal of this pattern above 50 years. This contrasted with incidence of schizophrenia that was almost twice as high in males as in females, particularly in the 20-29 year age group. Of 416 cases with a first-admission diagnosis of ATPD, an increasing number tended to change on subsequent admissions, nearly half to another F2 category schizophrenia and related disorders. The overall stability rate reached only 39%.
Conclusions: Although demographic differences from schizophrenia are topics that deserve further research, poor diagnostic stability argues against attempts to separate ATPD from borderland disorders.