Skip to main content

Verified by Psychology Today

Delirium, also referred to as "acute confusional state" or "acute brain syndrome," is a condition characterized by severe confusion and rapid changes in behavior and brain function. Delirium is distinct from dementia and usually much shorter in duration, though the two disorders share similar symptoms and may co-occur. Delirium comprises a cluster of symptoms—including reduced awareness, cognitive impairment, unusual behaviors, or emotional disturbances—that most often result from a treatable physical or mental illness. Delirium can also be a side effect of some medications.


Delirium’s primary symptoms involve disturbances in attention or awareness. In order to qualify as delirium, according to the DSM-5, these disturbances must:

  • Develop in a short time period (usually over the course of hours or a few days)
  • Represent a change from typical levels of attention and awareness
  • Tend to fluctuate in severity of the course of a day
  • Appear alongside an additional disturbance in cognition (such as in memory, language, perception, or orientation to time or place)

How these disturbances in attention or awareness manifest can vary between patients. Possible symptoms of delirium include, but aren’t limited to:

  • Difficulty concentrating on a specific topic of conversation or activity—or, conversely, becoming abnormally fixated on a topic or activity, even as others try to redirect
  • Rambling speech
  • Increased susceptibility to distraction
  • Appearing disoriented or confused
  • Difficulty recalling recent events
  • Sudden anxiety, euphoria, or anger
  • Dramatic mood swings
  • Apathy or depression
  • Sudden or unexplained drowsiness
  • Loss of motor control

For a diagnosis of delirium, such disturbances must not be better explained by a different neurocognitive disorder or occur during a low-arousal state such as a coma. Further, there must be evidence that the symptoms are the result of another medical condition, substance intoxication or withdrawal, exposure to a toxin, or other observable causes.

Delirium may coincide with a disturbance in the sleep-wake cycle (including, for example, sleepiness during the day and wakefulness at night) as well as in a person's emotional state, which may shift unpredictably. Patients with delirium can switch quickly between hyperactive states—characterized by restlessness, irritability, rapid mood changes, and combativeness—and hypoactive states, which are characterized by sluggishness, apathy, and other similar “low-energy” symptoms.

Delirium often lasts about one week in a hospital setting, but symptoms may persist for longer. Delirium can progress to coma or death, especially if the underlying cause is not treated.

How is delirium diagnosed?

Delirium is usually diagnosed via observation, a diagnostic interview, and careful monitoring of symptoms. Because symptoms of delirium can fluctuate rapidly and change throughout the day, doctors may observe a patient for a longer period to track symptom progress. In cases where drug or alcohol use, stroke, or other physical causes are suspected, doctors may also conduct blood tests, drug tests, X-rays, or brain scans to determine possible causes.

How long does delirium typically last?

Delirium can last anywhere from several hours to several months. How long delirium lasts usually depends on its cause and whether it is noticed and treated in a prompt manner. If treatment is initiated as early as possible, the recovery time may be shorter. 

article continues after advertisement

Delirium is usually the temporary result of a physical or mental illness. It can be caused by disorders that deprive the brain of oxygen or other substances or that result in the accumulation of toxins in the brain. Drug use, overdose, or withdrawal; infections, such as urinary tract infections; poisons; severe sleep deficits; and general anesthesia are among the varied causes of delirium. In many cases, treating the underlying cause will resolve symptoms of delirium, though recovery time may vary.

What is the most common cause of delirium?

Common causes of delirium include alcohol or drug withdrawal; certain medications; stroke; fever; malnutrition; infection (including urinary tract infections, sepsis, pneumonia, or the flu); severe sleep deprivation; surgery; or another medical condition such as liver disease, lung disease, and some chronic illnesses. Multiple factors may contribute to an episode of delirium.


Which medications can cause delirium?

Certain pain medications, sleep medications, psychiatric medications (especially those used to treat anxiety or depression), steroids, antihistamines, and medications used to treat Parkinson’s disease are among those that may trigger delirium. Patients taking these medications may wish to ask their doctor if delirium is a possible side effect.


Treatment varies depending on the specific condition causing delirium, and may require hospitalization.

Medications that worsen confusion—such as alcohol and illegal drugs, anticholinergics, analgesics, and central nervous system depressants, or others—may be stopped or changed. Medications or behavioral interventions may be used during treatment to control hazardous behaviors.

Tools for increasing orientation to one's surroundings and the use of eyeglasses and hearing aids may also be helpful for individuals with delirium.

What is the best treatment for delirium?

Determining the cause of delirium will guide the treatment plan in most cases. Beyond that, best practices for delirium include ensuring the patient is comfortable, safe, and has his or her physical and emotional needs met. This may include nutritional support, pain management, and, in some cases, medications to help manage mood or dangerous behaviors. Loved ones are often an important part of delirium treatment, as they can comfort the patient and help them keep calm during a confusing time.

How can future episodes of delirium be prevented?

Taking steps to address the underlying causes of a delirium episode may help prevent future ones. For example, if delirium was caused by sleep deprivation, promoting good sleep habits and maintaining a regular schedule could help. If medication was determined to be the cause of the delirium, the treatment plan should be reassessed with the help of a doctor. Elderly individuals, in particular, may benefit from regular movement, adequate fluid intake and nutritional support, and the use of hearing aids or glasses.

Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition
National Institutes of Health
Last updated: 07/07/2021