Hallucinations

False sensory perceptions (visual, auditory, olfactory, gustatory, tactile, or visceral) occurring in the absence of corresponding external stimuli, experienced with the vividness and immediacy of true perception and accompanied by a subjective conviction that the experience is real.

Causes

• Psychiatric and psychotic disorders

  • Schizophrenia spectrum disorders

  • Bipolar disorder

  • Major depressive disorder with psychotic features

• Neurological disorders

  • Neurodegenerative disorders: Alzheimer, Parkinson

  • Epilepsy

  • Migraine-associated hallucinations

  • Vision or hearing loss

  • Charles Bonnet syndrome

  • Brain lesions affecting sensory processing pathways

• Substance-related causes

  • Lysergic acid diethylamide (LSD)

  • Psilocybin

  • Cannabis

  • Stimulants (amphetamines, cocaine)

  • Alcohol withdrawal and delirium tremens

  • Sedatives

  • Corticosteroids

  • Dopamine agonists

• Sleep deprivation

• Hypnagogic or hypnopompic hallucinations

• Medical and systemic causes

  • Severe fever

  • Infection

  • Dehydration

  • Delirium due to acute illness

  • Metabolic disturbances

  • Organ failure-associated encephalopathy

• Sensory deprivation or isolation

• Extreme stress or exhaustion