Is the psychopathology of acute and transient psychotic disorder different from schizophrenic and schizoaffective disorders?

OBJECTIVE: This study explores psychopathological aspects of acute and transient psychotic disorders (ATPD), a diagnostic category introduced with ICD-10, to elucidate its relationship with schizophrenia and schizoaffective psychoses.
METHODS: We recruited all consecutive inpatients fulfilling the ICD-10 criteria of ATPD (F23) during a 5-year period as well as control groups with "positive" schizophrenia (PS) and bipolar schizoaffective disorder (BSAD) matched for gender and age at index episode. For the evaluation of psychopathological parameters during index episode a standardized symptom list was used. Prepsychotic (prodromal) symptoms were also assessed.
RESULTS: During the prepsychotic period few differences between the groups were detected. The most important difference between ATPD and the other two other psychotic disorders regarding phenomenology of the full-blown episodes was a higher frequency of "rapidly changing delusional topics", "rapidly changing mood" and anxiety in ATPD.
CONCLUSION: ATPD show a characteristic psychopathological picture consistent with earlier concepts such as cycloid psychoses and bouffée délirante. Nevertheless, psychopathology alone is not enough to establish ATPD as an independent nosological entity.