<prompt> Delusion is disorder ofThoughtPerceptionInsightBehaviour  <response>: Ans. a Thought. Ref. Short, Textbook of Psychiatry by Niraj Ahuja, 5th86 Delusion is a disorder of belief. Delusion is false unshakable belief, which is not keeping with patients socio-cultural educational background. These are of 2 types:- Primary- Secondary Primary delusions Autochthonous delusions- Arise de-novo cannot be explained on the basis of others experiences or perceptions.- Also known as autochthonous delusions, they are characteristic of schizophrenia are seen in its early stages. Secondary delusions- These are commonest delusions seen in clinical practice are not diagnostic of schizophrenia.- They are seen in other psychoses too.- These can be explained as arising from other abnormal experiences. 