Delusional disorder in the elderly

Definition. Persistent non-bizarre delusions lasting ≥1 month, without prominent hallucinations, disorganised speech or negative symptoms. Personality and functioning are relatively preserved.

Terminology and burden. Suspiciousness and paranoia affect 4–6% of older people. Onset at ≥60 years with schizophrenia-like features is termed very late-onset schizophrenia-like psychosis (VLOSLP); the older term is late paraphrenia.

Risk factors. Female sex, social isolation and living alone, never-married status, sensory impairment (deafness, poor vision), migrant status, premorbid paranoid or schizoid personality, and family history.

Subtypes. Persecutory (commonest), jealous (Othello), somatic (delusional infestation / Ekbom syndrome), erotomanic (de Clérambault), grandiose, and mixed.

Clinical features. Well-systematised, plausible delusions; partition delusions (belief that people or objects pass through walls, floors or ceilings) are characteristic of VLOSLP. Hallucinations, if present, are secondary. Insight is absent but daily function is maintained.

Differential diagnosis. Delirium, dementia (especially DLB and Alzheimer's disease), psychotic depression, drug-induced psychosis (levodopa, steroids, anticholinergics), alcohol/substance use, hypothyroidism, vitamin B12 deficiency, and temporal lobe lesions.

Evaluation. First-episode psychosis in old age always needs a full workup: CBC, sodium (mEq/L), calcium (mg/dL), glucose (mg/dL), renal and liver function, TSH, B12, VDRL/HIV, urine culture, complete drug review, cognitive testing (MMSE/MoCA), audiometry and vision assessment, and neuroimaging (CT/MRI brain).

Non-pharmacological management (first-line). Patient engagement and trust-building; correct sensory deficits — hearing aids, cataract surgery; reduce isolation through day care and community services; supportive psychotherapy and CBT for psychosis; carer education. In India — NPHCE day-care centres, Elder Line 14567, Tele-MANAS 14416.

Pharmacological management. Atypical antipsychotics preferred over conventional agents. Start low, go slow — roughly one-quarter to one-third of adult doses: risperidone 0.25–1 mg, olanzapine 2.5–5 mg, quetiapine 12.5–50 mg (drug of choice if parkinsonism or DLB), amisulpride 50–100 mg.

Adverse effects, monitoring, prognosis. Watch for EPS, tardive dyskinesia, falls, orthostatic hypotension, QTc prolongation, metabolic syndrome, and the boxed warning of increased stroke and mortality in dementia-related psychosis. Adherence is poor — consider long-acting injectables. Course is chronic but function is preserved; VLOSLP carries higher mortality than earlier-onset schizophrenia.

Xanomeline–trospium (KarXT, 2024–25). The first muscarinic M1/M4 agonist antipsychotic, FDA-approved in September 2024 for schizophrenia. Being non-dopaminergic, it causes no EPS, no prolactin rise and no weight gain — highlighted in the 2025 International Psychogeriatrics overview of late-onset psychoses as the most promising emerging option for older adults; trials in dementia-related psychosis are ongoing.

Antipsychotic evidence base reaffirmed. The ATLAS trial (Lancet Psychiatry) remains the only placebo-controlled RCT in VLOSLP — amisulpride 100 mg/day was superior to placebo over 12 and 24 weeks and well tolerated. The 2023 AGS Beers Criteria continue to classify antipsychotics as potentially inappropriate in older adults unless the indication is schizophrenia, bipolar disorder, or short-term antiemesis.