ICD-11 Criteria for Acute and Transient Psychotic Disorder (6A23) It characterises acute and transient psychotic disorder by acute onset of psychotic symptoms that emerge without a prodrome and reach their maximal severity within two weeks. Symptoms may include delusions, hallucinations, disorganisation of thought processes, perplexity or confusion, and disturbances of affect and mood. Catatonia-like psychomotor disturbances may be present. Symptoms typically change rapidly, both in nature and intensity, from day to day, or even within a single day. The duration of the episode does not exceed 3 months, and most commonly lasts from a few days to 1 month. The symptoms are not a manifestation of another medical condition (e.g. a brain tumour) and are not due to the effect of a substance or medication on the central nervous system (e.g. corticosteroids), including withdrawal (e.g. alcohol withdrawal).   6A23.0                     Acute and transient psychotic disorder, first episode