Although the mode of onset of schizophrenia can be acute, it is important to remember that the disorder rarely starts as a "clap of thunder in a quiet sky", and that it is more often gradual and insidious, with negative and affective symptoms. Acute and transient psychotic disorder, on the other hand, is a short delusional episode forming suddenly and lasting a few days, sometimes a few hours. Schizophrenic evolution forms only part of the possible evolutions. It is therefore necessary to disassociate acute and transient psychotic disorder from schizophrenic disorders, which gives a wrong representation of the onset of schizophrenia.