Background: The diagnostic category of acute and transient psychotic disorders (ATPD) was introduced in ICD-10. Subsequent studies have called into question its validity and reliability.
Aims: To determine the pattern of diagnostic revision to schizophrenia in first-ever diagnosed ATPD.
Method: Using data drawn from the Scottish Morbidity Record, we estimated incidence and diagnostic change in first-ever diagnosed ATPD in Scottish hospitals between January 1997 and December 2010 (n = 2923).
Results: The average incidence of ATPD was 4.1 per 100 000 population per year. Diagnostic stability was estimated at 53.9% over an average of approximately 4 years of observation. The most common diagnostic shift was to schizophrenia (12.6%), over an average of 1.7 years. Estimates of the transition risks for schizophrenia were 80% at 2.8 years and 90% at 4.6 years. Longer first admission to hospital, younger age at onset and male gender were associated with increased risk and earlier development of schizophrenia.
Conclusions: Routinely collected data suggest that approximately one in eight individuals with first-ever diagnosed ATPD will develop schizophrenia within 3-5 years. Those at high risk of transition may benefit from monitoring for possible diagnostic change.