What are the causes of psychosis in geriatric patients?

Causes of Psychosis in Geriatric Patients

Psychosis in elderly patients is most commonly caused by secondary medical conditions rather than primary psychiatric disorders, with approximately 60% of newly incident psychosis in older adults having an identifiable secondary cause. 1

Framework: The "Six D's" of Late-Life Psychosis

The diagnostic approach should systematically evaluate the following categories, as secondary causes must be ruled out before diagnosing primary psychosis 1:

1. Delirium

• Delirium is the most common cause of psychotic symptoms in elderly patients presenting to emergency departments 2
• Cardinal features include inattention, fluctuating consciousness throughout the day with lucid intervals, and acute onset over hours to days 2
• Infection (particularly urinary tract infections and pneumonia) is the most common precipitating factor 2
• Critical distinction: Unlike primary psychosis, delirium involves altered consciousness and disorientation, whereas psychosis typically maintains intact awareness and level of consciousness 2, 3
• Mortality doubles if delirium is missed, making early detection crucial 2
• Up to 10-31% of elderly patients have delirium at admission, developing in up to 56% of admitted patients 2

2. Disease (Medical Conditions)

Secondary medical causes that directly produce psychotic symptoms include 2:

• Endocrine disorders (thyroid dysfunction, Cushing's syndrome)
• Autoimmune diseases (lupus cerebritis, anti-NMDA receptor encephalitis)
• Neoplasms and paraneoplastic processes
• Neurologic disorders (stroke, traumatic brain injury, seizures including nonconvulsive status epilepticus)
• Infections (meningitis, encephalitis, systemic infections)
• Metabolic disorders (electrolyte imbalances, uremia, hepatic encephalopathy)
• Nutritional deficiencies (B12, thiamine)

3. Drugs (Medication-Induced)

Drug-related psychosis occurs through multiple mechanisms 2:

• Intoxication from medications or substances
• Withdrawal states (particularly alcohol and benzodiazepines, which can also cause life-threatening seizures) 4
• Side effects and toxicity from prescribed medications
• Elderly patients are particularly vulnerable due to polypharmacy and altered drug metabolism 5, 6

4. Dementia

• Psychotic symptoms occur commonly in patients with underlying dementia 2, 7
• Dementia-related psychosis has newly revised diagnostic criteria and represents a distinct clinical entity 7
• Sensory deficits (vision and hearing impairment) in elderly patients with cognitive decline can contribute to psychotic symptoms 6

5. Depression

• Depression with psychotic features is a primary psychiatric cause that must be distinguished from other etiologies 2, 3
• Mood-congruent delusions and hallucinations occur in the context of severe depressive episodes 3

6. Delusions (Primary Psychotic Disorders)

Primary psychiatric disorders causing psychosis in the elderly include 2, 3:

• Schizophrenia (both early-onset continuing into late life and late-onset presentations)
• Delusional disorder
• Schizoaffective disorder
• Bipolar disorder with psychotic features

Clinical Approach Algorithm

Step 1: Rule out medical emergencies

• Assess level of consciousness and orientation immediately 4, 3
• Perform focused neurological exam for focal deficits suggesting structural brain lesions 4
• Test for asterixis and myoclonus indicating metabolic encephalopathy 4

Step 2: Distinguish delirium from psychosis

• Evaluate for fluctuating consciousness, disorientation, and inattention (delirium) versus intact awareness (psychosis) 2, 4
• Missing this distinction is a critical pitfall that doubles mortality 2

Step 3: Investigate secondary causes systematically

• Review all medications and substances for intoxication, withdrawal, or adverse effects 2
• Evaluate for underlying medical conditions through appropriate laboratory and imaging studies 2
• Consider neuroimaging in new-onset psychosis to exclude intracranial processes requiring intervention 4, 3

Step 4: Diagnose primary psychosis only after exclusion

• Primary psychosis is a diagnosis of exclusion after ruling out all secondary causes 1
• Requires symptoms present for at least 6 months with marked functional deterioration 3
• Must rule out schizoaffective disorder and mood disorders with psychotic features 3

Key Clinical Pitfalls

• Don't assume primary psychiatric illness first - 60% of new psychosis in elderly patients has secondary causes 1
• Don't overlook withdrawal states - alcohol or benzodiazepine withdrawal requires immediate benzodiazepine treatment to prevent seizures 4
• Don't delay neuroimaging when focal neurological signs, head trauma history, or atypical features are present 4
• Don't miss the overlying organicity that complicates assessment more often in elderly than younger patients 6