Delusions in the general population: A systematic review with emphasis on methodology Søren Esben Rytter Heilskov a, * , Annick Urfer-Parnas a , Julie Nordgaard a, b a Mental Health Center Amager, Gl. Kongevej 33,1610, Copenhagen V, Denmark b Institute of Clinical Medicine, University of Copenhagen, Blegdamsvej 9, Copenhagen, Denmark article info Article history: Received 20 July 2019 Received in revised form 18 October 2019 Accepted 20 October 2019 Available online xxx Keywords: Psychosis Psychosis continuum Self-rated Delusion Review Psychopathology General population abstract 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 in- clusion 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 meth- odology relies with few exceptions exclusively on self-report and fully structured interview by lay per- son. 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. © 2019 Elsevier B.V. All rights reserved. Contents 1. Introduction ....................................................................................................................... 00 2. Methods ................................................................. ........................................................ 00 3. Results ............................................................................................................................ 00 3.1. Studies using a version of the composite international diagnostic interview (CIDI) (Andrews and Peters, 1998) .......................... 00 3.2. Studies using the Peters et al. Delusions Inventory-21 (PDI-21) (Peters et al., 1999, 2004) ........................ .................... 00 3.3. Studies using the community assessment of psychic experiences (CAPE) (Stefanis et al., 2002) ..................... .................. 00 3.4. Studies using the mini international neuropsychiatric interview (MINI) (Sheehan et al., 1998) ......................................... 00 3.5. Other studies ................................................................................................................ 00 4. Discussion ......................................................................................................................... 00 4.1. Limitations ............................................................. .................................................... 00 4.2. Conclusion ............................................................. .................................................... 00 Acknowledgement ................................................................................................................. 00 References ........................................................................................................................ 00 1. Introduction Delusions are considered a key feature of psychosis, distinguishing normality from pathology, but recent reports sug- gesting that delusions are common in the general population are challenging the traditional categorical perception of psychotic illness. In the current diagnostic systems, the presence of delusions remains one of the main criteria for psychotic disorders (American * Corresponding author. Gl. Kongevej 33, 1610, Copenhagen V, Denmark. E-mail address: esben_rytter@hotmail.com (S.E.R. Heilskov). Contents lists available at ScienceDirect Schizophrenia Research journal homepage: www.elsevier.com/locate/schres https://doi.org/10.1016/j.schres.2019.10.043 0920-9964/© 2019 Elsevier B.V. All rights reserved. Schizophrenia Research xxx (xxxx) xxx Please cite this article as: Heilskov, S.E.R et al., Delusions in the general population: A systematic review with emphasis on methodology, Schizophrenia Research, https://doi.org/10.1016/j.schres.2019.10.043