Delusion is a fixed, false belief that is held with strong conviction despite clear or obvious evidence to the contrary. These beliefs are not accounted for by the patient’s cultural or religious background and are usually pathognomonic of a psychiatric or neurological disorder.

Common types of delusions include:

• Delusion of grandeur: Exaggerated belief in one’s own importance, wealth, or abilities; the patient may identify with powerful historical or fictional figures (e.g., Napoleon).

• Paranoid (persecutory) delusion: Belief that one, or someone close, is being targeted, harassed, or conspired against.

• Somatic delusion: Belief that one’s body is diseased, abnormal, or altered in function or structure.

Delusions frequently occur in schizophrenia, schizoaffective disorder, bipolar disorder, major depression with psychotic features, and other psychotic syndromes.

Pathophysiology

The mechanisms underlying delusions are complex and involve dysregulation in brain networks responsible for belief formation, reality testing, and sensory integration.

• Neurotransmitter dysregulation:

  • Dopaminergic hyperactivity, particularly in mesolimbic pathways, contributes to abnormal salience attribution and belief fixation.

  • Glutamatergic and serotonergic disturbances may affect perception and reasoning.

• Structural and functional brain changes:

  • Alterations in the prefrontal cortex, temporal lobes, and limbic system impair judgment, insight, and reality monitoring.

• Cognitive biases:

  • Abnormalities in reasoning and probabilistic thinking reinforce false beliefs.

• Environmental and psychosocial factors:

  • Trauma, stress, or social isolation may exacerbate the formation and persistence of delusions.

Examination Technique

Clinical Observation

• Assess speech content and coherence for evidence of fixed false beliefs.

• Observe for emotional congruence or incongruence with expressed beliefs.

• Evaluate insight by gently challenging beliefs and noting the patient’s response.

Structured Assessment

• Use psychopathology rating scales such as the Positive and Negative Syndrome Scale (PANSS) or Brief Psychiatric Rating Scale (BPRS) to quantify severity.

• Document type, intensity, conviction, and impact on function.

Clinical Features

Differential Diagnosis

Pediatric considerations

• Rare; usually secondary to autism spectrum disorder, psychotic disorders, or medical illness.

• Careful evaluation is needed to differentiate from magical thinking or age-appropriate fantasy.

Geriatric considerations

• May occur in dementia, delirium, or late-onset psychosis.

• Often associated with visual or auditory impairment and social isolation.

• Requires careful assessment for medical, neurological, and psychiatric contributors.

Limitations

• Cultural or religious beliefs may mimic delusional thinking; always consider context.

• Patients often lack insight, complicating assessment and treatment adherence.

Patient counseling

• Explain that delusions are symptoms of an underlying disorder rather than intentional falsehoods.

• Emphasize the importance of medical and psychiatric evaluation.

• Discuss treatment options, including antipsychotics, psychotherapy, and support for caregivers.

• Provide reassurance about safety, monitoring, and gradual improvement with appropriate therapy.

Management

Pharmacological

• First-line: Antipsychotics (e.g., risperidone, olanzapine, haloperidol).

• Adjuncts: Mood stabilizers if delusions are mood-congruent.

Non-Pharmacological

• Cognitive-behavioral therapy (CBT) for psychosis may help reduce distress and improve reality testing.

• Psychoeducation and social support for patients and caregivers.

• Monitor for risk of harm to self or others.

Conclusion

Delusions are persistent false beliefs resistant to contrary evidence, commonly observed in psychiatric disorders such as schizophrenia and bipolar disorder. Early recognition, targeted pharmacologic and psychosocial interventions, and careful monitoring are crucial for symptom control, functional improvement, and patient safety.

References

1. American Psychiatric Association. DSM-5: Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington, VA: APA; 2013.

2. Freeman D. Delusions in the general population. Curr Psychiatry Rep. 2006;8:191–204.

3. Kahn RS, Keefe RS. Schizophrenia is a cognitive illness: Time for a change in focus. JAMA Psychiatry. 2013;70:1107–1112.

4. Tandon R, et al. Definition and description of schizophrenia in the DSM-5. Schizophr Res. 2013;150:3–10.

5. Garety PA, Freeman D. The past and future of delusions research: From the inexplicable to the treatable. Br J Psychiatry. 1999;174:366–373.