Delirium is a severe but usually temporary state of confusion.


Delirium is a condition of severe confusion and rapid changes in brain function. Delirium in itself is not a disease, but rather a cluster of symptoms that may result from a disease or other clinical process. Shorter in duration than dementia, it is often the result of treatable physical or mental illness. Underlying causes should be investigated. Delirium can be a side effect of some medications. Delirium is also referred to as "acute confusional state" or "acute brain syndrome."


Delirium involves a rapid alternation between mental states (for example, from lethargy to agitation and back to lethargy).

Symptoms include:

  • Disrupted or wandering attention
  • Inability to think or behave with purpose
  • Disorganized thinking
  • Speech that doesn't make sense (incoherence)
  • Inability to stop speech patterns or behaviors
  • Confusion or disorientation about time or place
  • Changes in feeling (sensation) and perception
  • Changes in level of consciousness or awareness
  • Changes in sleep patterns, drowsiness
  • Changes in alertness (significantly more alert in morning, less alert at night)
  • Decrease in short-term memory and recall
  • Unable to remember events since the delirium began (anterograde amnesia)
  • Unable to remember past events (retrograde amnesia)
  • Changes in movement (for example, may be inactive or slow moving)
  • Movements triggered by changes in the nervous system

Emotional or personality changes including:

  • Anxiety
  • Anger
  • Apathy
  • Depression
  • Euphoria
  • Irritability

Complications include:

  • Loss of ability to function or care for self
  • Loss of ability to interact effectively with others
  • Progression to stupor or coma
  • Side effects from the medications used to treat the disorder


Acute confusional states are usually the result of a physical or mental illness and are typically temporary and reversible.

Disorders that cause delirium are numerous and varied. They may include conditions that deprive the brain of oxygen or other substances. Delirium may be caused by diseases of body systems other than the brain; drug abuse; infections, such as urinary tract infections; poisons; fluid/electrolyte or acid/base disturbances; and by other serious, acute conditions.

Neurological examination may reveal abnormalities, including atypical reflexes. Results of psychological studies and tests of sensation, cognitive function, and motor function may be abnormal.


The goal of treatment is to control or reverse symptoms. Treatment varies with the specific condition causing delirium. Diagnosis and care should take place in a pleasant, comfortable, nonthreatening, physically safe environment. Hospitalization may be required for a short time.

Stopping or changing medications that worsen confusion, or that are not essential to the care of the person, may improve cognitive functioning even before treatment of the underlying disorder. Medications that may exacerbate confusion include alcohol and illegal drugs, anticholinergics, analgesics, cimetidine, central nervous system depressants, lidocaine, and other medications.

Disorders that contribute to confusion should be treated. These may include heart failure, decreased oxygen (hypoxia), high carbon dioxide levels (hypercapnia), thyroid disorders, anemia, nutritional disorders, infections, kidney failure, liver failure, and psychiatric conditions such as depression. Treating medical and psychiatric disorders often greatly improves mental functioning.

Medications may be required to control aggressive or agitated behaviors that are dangerous to the patients or to those around them. These are usually given in very low doses, with adjustment as required.

Medications that may be considered for use include: thiamine; sedating medications (such as clonazepam or diazepam; serotonin-affecting drugs (trazodone, buspirone); dopamine blockers (such as haloperidol, olanzapine, risperidol, and clozapine); and mood stabilizers (fluoxetine, imipramine, celexa).

Some people with delirium may benefit from hearing aids, glasses, or cataract surgery.

Formal psychiatric treatment may be necessary. Behavior modification might help some people control unacceptable or dangerous behaviors. This technique consists of rewarding appropriate or positive behaviors and ignoring inappropriate behaviors (within the bounds of safety). Reality orientation, with repeated reinforcement of environmental and other cues, may help reduce disorientation.

Acute disorders that cause delirium may coexist with chronic disorders that cause dementia. Acute brain syndromes are potentially reversible with treatment of the underlying cause. Delirium often lasts only about one week, although it may take several weeks for cognitive function to return to normal levels. Full recovery is common.


  • National Institutes of Health
  • U.S. National Library of Medicine

Last reviewed 02/07/2019