An acute psychotic disorder in which hallucinations, delusions or perceptual disturbances are obvious but markedly variable, changing from day to day or even from hour to hour. Emotional turmoil with intense transient feelings of happiness or ecstasy, or anxiety and irritability, is also frequently present. The polymorphism and instability are characteristic for the overall clinical picture and the psychotic features do not justify a diagnosis of schizophrenia. These disorders often have an abrupt onset, developing rapidly within a few days, and they frequently show a rapid resolution of symptoms with no recurrence. If the symptoms persist the diagnosis should be changed to persistent delusional disorder.