Delusional disorder in older adults

Contributed by: Patricia To MD, FRCPC, BSc Pharm – View Dr. To’s bio

Case

Monique is a 63-year-old female who was referred to geriatrics by her family physician with presenting concerns of worsening memory and attention. On brief cognitive testing, she scored 29/30 on the Montreal Cognitive Assessment (MoCA).¹ This would be considered normal. Functionally, she lives independently, does her own grocery shopping and banking, and is a retired administrative assistant. Her past medical history is relevant for Type 2 diabetes, hypertension, dyslipidemia and insomnia.

During her appointment, she describes that over the last year she has noticed her memory and ability to focus have significantly worsened. Examples she provides include that she cannot recall her grocery list when shopping, forgets what she wants to do when she goes into the next room and finds it difficult to focus on her favourite television program or on reading the newspaper.

The interview quickly turns to how her life has changed following her new neighbours moving in 1.5 years ago. She is quite fixated, perseverative and adamant that they have installed cameras in her house to monitor her. She believes this is part of a plan to break into her home, steal her belongings and force her to move so they can purchase the property.

What could be going on?

Issue

How can delusional disorder present and be managed in older adults?

Background

Delusional disorder is defined in the DSM‑V by the presence of one or more delusions lasting at least one month, with overall minimal functional impairment aside from the impact of the delusion.² A delusion is a fixed, false belief that is based on an inaccurate interpretation of reality and external events, and remains unaltered despite presentation of conflicting or contrary evidence.³ 

The lifetime prevalence of delusional disorder according to the American Psychiatric Association (APA) is low in comparison to other psychotic disorders, at 0.02%, with the most common subtype being persecutory.² However, this is likely a gross underestimation given the nature of the disorder. Specifically, the criteria of delusional disorder require limited functional impairment, meaning a significant portion of individuals with this disorder are not presenting to medical attention.

Evidence

In regard to older adults, the prevalence of delusional disorder has been estimated to be approximately double that estimated by the APA, at 0.04%, as found in an epidemiological cohort study examining delusional disorder in adults aged 65 years or older.⁴

This is in keeping with the higher incidence of psychosis in older adults secondary to a variety of factors unique to this demographic including age-related degeneration of the cerebral cortex, particularly areas of the frontal and temporal lobes; neurochemical changes that occur with ageing; sensory deficits; changes in cognitive function; life changes; and social factors contributing to increased isolation and polypharmacy.⁵

It is important to screen for safety concerns that may be influenced by the underlying delusion, including physical and mental safety, risk of deterioration and suicidal or homicidal ideation. Based on the presence of safety concerns, this may lead to prioritization of hospitalization, potentially under the Mental Health Act.

Antipsychotics have been the mainstay of treatment for delusional disorder, which is no different in older adults despite the paucity of controlled trials to support this practice.⁶ With the development of atypical antipsychotics such as risperidone, these agents have been utilized more frequently than typical antipsychotics. However, Manschrek et al. found atypical and typical antipsychotics performed similarly, although this conclusion is limited by the quality of the studies and notable lack of controlled trials.⁷

Therefore, the consideration for an appropriate antipsychotic agent may be best influenced by the patient’s medical history, current medications and the medication’s side-effect profile. Antidepressants and mood stabilizers are less commonly used in the management of delusional disorder but are noted in the literature. Their role likely relates to the treatment of comorbid conditions when present.⁶

The treatment of delusional disorder is challenging due to the patient’s limited insight, in combination with generally intact function and baseline safety. This can make it difficult to challenge decision-making capacity and to engage patients meaningfully in treatment. 

Treatment in older adults is further complicated by the higher likelihood of underlying comorbidities, increased sensitivity to medication side effects and the impact of age-related cognitive changes and underlying cortical degeneration on clinical presentation.⁸

Accordingly, the decision to treat requires careful consideration of potential benefits, such as improvements in quality of life, symptom burden and functional impairment. These must be weighed against the risks of antipsychotic use in older adults, which include but are not limited to cerebrovascular and cardiovascular events, cognitive deficits and infections.⁹

Nagendra et al. studied delusional disorder in hospitalized older adults and found that with treatment with antipsychotic medication, the majority improved, and 20% had sustained recovery.⁹ Interestingly, only a minority went on to subsequently develop dementia, which challenges the widely accepted belief that delusional disorder in later life may be a herald for dementia. However, this finding is likely limited by the study’s duration, small sample size and the controlled inpatient environment.¹⁰

This study was conducted in a hospital setting indicating a likely degree of clinical severity and safety concerns warranting inpatient treatment. In contrast, there are unique challenges in engaging patients with delusional disorder in the community with ongoing treatment. 

One narrative review focused on adherence to antipsychotic medication in females with delusional disorder identified relevant patient factors, including underlying personality, intensity of delusions, perception of side effects and cognitive impairment.¹¹ The authors recommended that clinicians focus on time spent with the patient, clarity of communication and close treatment monitoring to enhance the therapeutic alliance, patient buy-in and, therefore, adherence to treatment.¹¹

Engagement with psychotherapeutic interventions is recommended and would likely lead to better outcomes when combined with medication, but can be compromised by the patient’s limited insight, which can reduce their interest and engagement.^3,8

Conclusion

A diagnosis of delusional disorder requires a comprehensive evaluation and management plan that includes investigations for contributing organic or medical factors, review of psychosocial stressors and exploration of one’s underlying nature and personality. Altogether, this can help clinicians understand why a particular individual is presenting with this condition, and which corresponding interventions may be most appropriate.

Helpful resource

Centre for Addiction and Mental Health (CAMH). Delusional Disorder

References 

1. Nasreddine ZS, Phillips NA, Bédirian V, Charbonneau S, Whitehead V, Collin I, Cummings JL, Chertkow H. The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005 Apr;53(4):695-9. doi: 10.1111/j.1532-5415.2005.53221.x. Erratum in: J Am Geriatr Soc. 2019 Sep;67(9):1991. doi: 10.1111/jgs.15925. PMID: 15817019.
2. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington (VA): American Psychiatric Publishing; 2013.
3. Joseph SM, Siddiqui W. Delusional Disorder [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan– [updated 2023 Mar 27; cited 2025 Oct 14]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539855/
4. Copeland JR, Dewey ME, Scott A, Gilmore C, Larkin BA, Cleave N, et al. Schizophrenia and delusional disorder in older age: Community prevalence, incidence, comorbidity, and outcome. Schizophr Bull. 1998;24(1):153–61. doi:10.1093/oxfordjournals.schbul.a033307
5. Karim S. Diagnosis and management of psychosis in older people. Prescriber. 2008;19(2):38–43. Available from: https://wchh.onlinelibrary.wiley.com/doi/pdf/10.1002/psb.181
6. Skelton M, Khokhar WA, Thacker SP. Treatments for delusional disorder. Cochrane Database Syst Rev. 2015;2015(5):CD009785. doi:10.1002/14651858.CD009785.pub2
7. Manschrek T, Khan N. Recent advances in the treatment of delusional disorder. Can J Psychiatry. 2006;51(2):114–9.
8. Lapid MI, Ho JB. Challenging our beliefs about delusional disorder in late life. Int Psychogeriatr. 2020;32(4):423–5. doi:10.1017/S1041610219001352
9. Steinberg M, Lyketsos CG. Atypical antipsychotic use in patients with dementia: managing safety concerns. Am J Psychiatry. 2012;169(9):900–6.
10. Nagendra J, Snowdon J. An Australian study of delusional disorder in late life. Int Psychogeriatr. 2019;32(4):453–62.
11. González-Rodríguez A, Monreal JA, Seeman MV. Factors influencing adherence to antipsychotic medications in women with delusional disorder: A narrative review. Curr Pharm Des. 2022;28(15):1282–93. doi:10.2174/138161282866622031015162