Causes

Delirium occurs when the normal sending and receiving of signals in the brain become impaired. This impairment is most likely caused by a combination of factors that make the brain vulnerable and trigger a malfunction in brain activity.

Delirium may have a single cause or more than one cause, such as a combination of a medical condition and drug toxicity. Sometimes no cause can be identified. Possible causes include:

• Certain medications or drug toxicity
• Alcohol or drug intoxication or withdrawal
• A medical condition, such as a stroke, heart attack, worsening lung or liver disease, or an injury from a fall
• Metabolic imbalances, such as low sodium or low calcium
• Severe, chronic or terminal illness
• Fever and acute infection, particularly in children
• Urinary tract infection, pneumonia or the flu, especially in older adults
• Exposure to a toxin, such as carbon monoxide, cyanide or other poisons
• Malnutrition or dehydration
• Sleep deprivation or severe emotional distress
• Pain
• Surgery or other medical procedures that include anesthesia

Several medications or combinations of drugs can trigger delirium, including some types of:

• Pain drugs
• Sleep medications
• Medications for mood disorders, such as anxiety and depression
• Allergy medications (antihistamines)
• Asthma medications
• Steroid medicines called corticosteroids
• Parkinson's disease drugs
• Drugs for treating spasms or convulsions