15th February 2025

Delusional disorder

Delusional disorder is defined by the ICD-11 as the ‘presence of a delusion or set of related delusions, typically persisting for at least 3 months or often much longer, in the absence of a depressive, manic or mixed episode.’ Delusions are ‘variable in content across individuals, while showing remarkable stability within individuals, although they may evolve over time.’ 

Characteristic symptoms of schizophrenia (e.g. persistent hallucinations, formal thought disorder, negative symptoms, and experiences of influence, passivity or control) will be absent. However, specific hallucinations typically related to the delusion may be present. Affect, speech and behaviour are typically unaffected, apart from when directly related to the delusions.

Eponymous and miscellaneous delusional conditions

Table 4 Eponymous and miscellaneous delusional conditions (Sims’ Symptoms in the Mind)

References

• British National Formulary. Psychoses and related disorders. Online [cited 16 January 2022]. Available from: https://bnf.nice.org.uk/treatment-summary/psychoses-and-related-disorders.html 
• ICD-11. Schizophrenia. Online [cited 17 December 2023]. Available at: https://icd.who.int/browse11/l-m/en#/http%3a%2f%2fid.who.int%2ficd%2fentity%2f1683919430
• ICD-11. Schizoaffective Disorder. Online [cited 17 December 2023]. Available at: https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/106339515
• National Institute for Health and Care Excellence. Psychosis and schizophrenia: what monitoring is required? [Internet]. NICE. September 2021 [cited 17 December 2023]. Available from: https://cks.nice.org.uk/topics/psychosis-schizophrenia/prescribing-information/monitoring/ 
• Oyebode F. Delusions and Other Erroneous Ideas. In: Sims’ Symptoms in the Mind. Edinburgh: Elsevier; 2018. Pp. 105-128
• Schizophrenia and Related Psychoses. In: Oxford Handbook of Psychiatry. 4th ed. Ed. Semple D and Smyth R. Oxford: Oxford University Press; 2019. Pp 179-241