Background: We examined whether acute transient psychoses can be distinguished from schizophrenia and the affective disorders.
Method: We studied 46 cases of nonaffective acute psychosis in the Chandigarh Acute Psychosis Study. With respect to separation from schizophrenia, we examined the distribution of duration of the episode. With respect to separation from affective disorders, we assessed the frequency of affective symptoms.
Results: Duration was bimodal, suggesting the presence of two distinct conditions of short and long duration. Affective symptoms were minimal, suggesting that these were not atypical affective syndromes.
Conclusions: Acute transient psychoses conform neither with schizophrenia of brief duration nor with atypical affective psychosis, and thus require separate classification as proposed in the ICD-10.