People at higher risk of delirium include older adults and people:

  • With cognitive diseases, like dementia
  • With disabilities or multiple diseases
  • Undergoing surgery

Reversible Causes of Delirium

Delirium can have one cause or multiple causes. Treating just one cause probably won’t be enough. All possible causes need treatment when possible. The healthcare provider needs to find as many causes as possible and treat those that are reversible.

These causes are related to:

  • Drugs, including:
    • New medications or higher dosages of existing drugs
    • Drug interactions
    • Over-the-counter drugs, alcohol use or withdrawal, illegal drugs 
    • Drugs that reduce the amount of acetylcholine (a chemical that carries the brain’s electrical signals) are more likely to cause delirium. These drugs include medications used for anxiety, sleep, pain, depression, and allergies.  
  • Electrolyte disturbances, fluid imbalances and thyroid problems. Examples of electrolytes are salt and calcium.
  • Lack of drugs, like when long-term sedatives (for example, alcohol and sleeping pills) are stopped too suddenly, or when the amount of pain drugs isn’t enough.
  • Infection, commonly urinary, respiratory tract, or skin infection. 
  • Reduced sensory input, which happens when vision or hearing are poor.
  • Intracranial (referring to processes within the skull) problems such as a brain infection, hemorrhage, stroke, or tumor (rare). Head injuries, such as from a fall, can also cause delirium.
  • Urinary problems or intestinal problems, such as constipation or inability to urinate.
  • Myocardial, heart and lung diseases. 


Delirium can also come from:

  • An imbalance in brain chemicals through use of medications, presence of dementia, and other conditions. 
  • Almost any physical illness, especially when a person has more than one.
  • Changes in the person’s surroundings (environment) or too little sensory input because of vision and hearing loss.


Last Updated May 2023

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