What is the difference between psychosis and delirium?

Distinguishing Delirium from Psychosis

The critical difference is that delirium involves altered consciousness, inattention, and disorientation with acute fluctuating onset, while psychosis maintains intact awareness and level of consciousness despite the presence of hallucinations and delusions. 1, 2

Key Distinguishing Features

Delirium Characteristics

• Inattention is the cardinal feature that must be present for diagnosis 1
• Fluctuating consciousness throughout the day with lucid intervals 1
• Acute onset developing over hours to days 2
• Disorientation to time, place, or person 2
• Altered level of arousal (either hyper- or hypoactive) 3
• Symptoms directly precipitated by underlying medical causes: infection (most common—UTI or pneumonia), intoxication, toxin exposure, withdrawal, or metabolic derangements 1

Psychosis Characteristics

• Awareness and level of consciousness remain intact—this is the most important differentiator 1, 2
• Delusions and hallucinations are cardinal features 1
• Disorganized speech or thought patterns 1
• Disorganized or abnormal motor behavior (catatonia, agitation) 1
• Negative symptoms such as diminished emotional expression 1
• Can be primary (schizophrenia, bipolar disorder, schizoaffective disorder, depression with psychotic features) or secondary (medical conditions, substance-related) 1

Clinical Urgency and Mortality Impact

Delirium is a medical emergency where missing the diagnosis doubles mortality risk. 1, 2 Early detection is critical as mortality in patients with acute mental status changes is approximately 8.1%, significantly higher in elderly patients 1. Up to 10-31% of patients have delirium at admission, developing in up to 56% of admitted patients, particularly post-surgery or in ICU settings 1.

Diagnostic Approach Algorithm

Step 1: Assess Level of Consciousness and Attention

• If consciousness is altered or fluctuating, or inattention is present → suspect delirium 1, 2
• Use validated tools: Confusion Assessment Method (CAM), CAM-ICU, or B-CAM 1
• If consciousness and attention are intact → consider psychosis 1, 2

Step 2: Determine Temporal Course

• Acute onset over hours to days with fluctuation → delirium 2
• Symptoms present for weeks to months with more stable course → psychosis 4

Step 3: Identify Precipitating Factors

For delirium, systematically evaluate for:

• Infection (urinary tract, pneumonia—most common) 1
• Metabolic derangements (electrolytes, glucose, hepatic/renal dysfunction) 2
• Medications or toxins 1
• Withdrawal states (alcohol, benzodiazepines) 1, 2
• Intracranial processes (stroke, hemorrhage, mass) 1

For psychosis, distinguish primary versus secondary:

• Secondary causes: endocrine disorders, autoimmune diseases, neoplasms, neurologic disorders, infections, metabolic disorders, nutritional deficiencies, drug intoxication/withdrawal 1, 2
• Primary causes: psychiatric disorders (schizophrenia, bipolar, schizoaffective, depression with psychotic features) 1

Step 4: Rule Out Co-occurrence

Critical pitfall: Delirium and psychosis can coexist, particularly in conditions like delirious mania 5. The presence of psychotic symptoms does not exclude delirium—always assess for altered consciousness and inattention 5.

Common Diagnostic Pitfalls

• Don't assume intact speech means intact consciousness—patients with hyperactive delirium may appear conversant but demonstrate profound inattention upon formal testing 1
• Don't overlook hypoactive delirium—subtle disturbances in consciousness make detection difficult and are easily missed 1
• Don't attribute confusion solely to psychosis in elderly patients—delirium is the most common cause of psychotic symptoms in elderly ED presentations 2
• Don't delay treatment of withdrawal states—these require immediate benzodiazepine treatment to prevent seizures 2
• Don't forget that two or more precipitating causes frequently coexist in delirium 1

Management Implications

Delirium Management

• Treat the underlying medical cause (infection, metabolic derangement, etc.) 1
• Nonpharmacological approaches first (reorientation, sleep hygiene, mobilization) 1
• Antipsychotics only when necessary for agitation or psychotic symptoms that pose safety risk 3
• Effective after-care planning 1

Psychosis Management

• For secondary psychosis: treat underlying medical cause and control psychotic symptoms 1, 2
• For primary psychosis: antipsychotic medications, psychological therapy, and psychosocial interventions 1, 4
• Atypical antipsychotics preferred over first-generation agents due to lower extrapyramidal symptom risk 6

Special Considerations in Elderly Patients

Delirium is the most common cause of psychotic symptoms in elderly patients presenting to emergency departments. 2 Prevalence of psychotic disorders due to general medical conditions is higher in those ≥65 years 1. Late-onset psychosis carries higher morbidity and mortality than early-onset psychosis and requires careful low-dose initiation of antipsychotics with close monitoring 7.