Objective – Delusions and lack of insight have traditionally been viewed as the defining characteristics of insanity and in modern psychiatry continue to be central to the diagnosis of psychosis. Little is known about the mechanisms of delusion formation and much of the research into delusions and lack of insight has been focussed on schizophrenia, in spite of the fact that these symptoms are also prominent in other disorders e.g., affective psychosis. The objective of this paper is to review the literature on existing theories of delusions and insight with reference to the effects of affective disturbance on memory processes. Method – Narrative review supplemented by literature searches using Medline, PsycINFO and EMBASE databases for the period 1980 to present using terms “delusion”, “insight” and “affect”. Results – The role of affect on memory in normal psychology and delusions in psychopathology is being increasingly recognised. We sketch out a theory which gives weight to locating the formation and maintenance of mood congruent and mood incongruent delusional beliefs (and insight into such beliefs) within a model of normal memory processes. Conclusion – We conclude that delusional beliefs may represent false or biased memories of internal or external events modified and strengthened of by affective states. We propose that insight rests on an ability to identify these memories as internally generated or biased. In view of the growing body of knowledge accumulating from the study of memory, emotion and their neuropsychological correlates we would suggest using this as an evidence base for the further neuropsychiatric investigation of delusional beliefs.

Declaration of Interest: none.