The relationship of reactive psychosis and ICD-10 acute and transient psychotic disorders: evidence from a case register-based comparison

BACKGROUND: ICD-10 introduced a new diagnostic category, F23 'acute and transient psychotic disorders' (ATPD), to embrace clinical concepts such as bouffée délirante, cycloid psychosis, psychogenic (reactive) psychosis and schizophreniform psychosis. The purpose of this study was to examine the relationship between the concept of reactive psychosis (RP), equivalent to the ICD-8 298 category of 'other psychoses', and ATPD. SAMPLING AND METHOD: Since January 1, 1994, ICD-10 has replaced ICD-8 as official classification in Denmark. Patients given an ICD-8 298 diagnosis on their last admission in 1992-1993 were identified from the Danish Psychiatric Central Register, and the ICD-8 diagnoses assigned were compared with their ICD-10 diagnoses when readmitted in 1994-1995. RESULTS: Diagnosis of RP was recorded in 19.2% of patients with functional psychoses in 1992-1993, whereas ATPD overall prevalence accounted for 8.7% of those with non-organic psychotic and affective disorders in 1994-1995. Thirty-eight per cent of patients with an ICD-8 298 diagnosis were readmitted during the years 1994-1995. Schizophrenia and related disorders (F2) and affective disorders (F3) accounted for three quarters of ICD-10 diagnoses. The most frequently used ATPD subcategories were F23.3 'other acute delusional psychotic disorders', F23.0 'acute polymorphic psychotic disorder without symptoms of schizophrenia' and F23.9 'acute and transient psychotic disorder unspecified'. A significant majority were female and associated acute stress was recorded only in 5.3% of cases. CONCLUSIONS: ICD-8 298 register diagnosis of RP showed little empirical continuity to ATPD and conformed more to F23.3 acute delusional disorder among ATPD subtypes.