Delusions in the general population: A systematic review with emphasis on methodology

The presence of delusions is considered a key feature of psychosis, but despite the psychopathological centrality of the concept of delusion, its definition and comprehension is a matter of continuing debate. In recent years studies showing that delusions are common in the general population have accumulated and challenged the way we perceive psychotic illness. In this systematic review, we examine the basis of the psychosis continuum-hypothesis, by reviewing a representative section of the original literature that report measures of delusional ideation in the general population, focusing specifically on methodology. Three online databases were systematically searched for relevant studies. After applying criteria of inclusion and exclusion, 17 articles were included for comprehensive review. Estimates of the distribution of delusions in the general population vary substantially, as does the mode of assessment. The methodology relies with few exceptions exclusively on self-report and fully structured interview by lay person. We conclude that measures of delusions in the general population should be interpreted cautiously due to inherent difficulties in methodology. Hypothesizing a continuum of delusion between normality and full-blown psychosis is deemed premature based on the reviewed studies.