Clinical concepts regarding atypical psychosis such as the French bouffeé délirante, the German cycloid psychosis, and the Scandinavian reactive and schizophreniform psychoses are now under the category of F23 ‘Acute and transient psychotic disorders’ (ATPD) of the tenth revision of the International Classification of Mental and Behavioural Disorders (ICD-10).

The authors’ aim is to highlight the clinical and scientific relevance of atypical psychosis from the historical concepts to the current perspective.

A Pubmed database search using as keywords “atypical psychosis”, “acute and transient psychotic disorders”, and “brief psychotic disorder” and retrieved papers were selected according to their relevance.

Different psychiatric schools, often of a regional or national character, have provided concepts for transient psychotic states. The acute and transient psychotic disorders of ICD-10 and the brief psychotic disorder of Diagnostic and Statistical Manual of Mental Disorders (DSM-5) reflect the diversity of the history of such concepts. The available evidence suggests that case identification and follow-up is difficult in ATPD due to the heterogeneous and infrequent nature of this clinical phenomenon. Furthermore ATPD has a low diagnostic stability and there are few studies focused on brief psychotic disorders.

The present definition of acute and transient psychotic disorders and brief psychotic disorder, while taking into account the history of the concepts involved, leave many questions open to further studies.

The authors have not supplied their declaration of competing interest.