Delirium is a serious disturbance in a person's mental abilities that results in a decreased awareness of one's environment and confused thinking. The onset of delirium is usually sudden, often within hours or a few days.

Delirium can often be traced to one or more contributing factors, such as a severe or chronic medical illness, medication, infection, surgery, or drug or alcohol abuse.

The symptoms of delirium and dementia can be similar, and input from a family member or caregiver may be important for a doctor to make an accurate diagnosis.

Symptoms Causes Complications Prevention

The signs and symptoms of delirium appear over a short period of time, from a few hours to a few days. They often fluctuate throughout the day, so a person may have periods of no symptoms. Primary signs and symptoms include those below.

Reduced awareness of the environment

This may result in:

  • An inability to stay focused on a topic or to change topics
  • Wandering attention
  • Getting stuck on an idea rather than responding to questions or conversation
  • Being easily distracted by unimportant things
  • Being withdrawn, with little or no activity or little response to the environment

Poor thinking skills (cognitive impairment)

This may appear as:

  • Poor memory, particularly of recent events
  • Disorientation, or not knowing where one is, who one is or what time of day it is
  • Difficulty speaking or recalling words
  • Rambling or nonsense speech
  • Difficulty understanding speech
  • Difficulty reading or writing

Behavior changes

  • Seeing things that don't exist (hallucinations)
  • Restlessness, agitation, irritability or combative behavior
  • Disturbed sleep habits
  • Extreme emotions, such as fear, anxiety, anger or depression

Delirium and dementia

Other medical conditions can result in symptoms associated with delirium. Dementia and delirium may be particularly difficult to distinguish, and a person may have both. In fact, frequently delirium occurs in people with dementia.

Dementia is the progressive decline of memory and other thinking skills due to the gradual dysfunction and loss of brain cells. The most common cause of dementia is Alzheimer's disease.

Some differences between the symptoms of delirium and dementia include:

  • Onset. The onset of delirium occurs within a short time, while dementia usually begins with relatively minor symptoms that gradually worsen over time.
  • Attention. The inability to stay focused or maintain attention is significantly impaired with delirium. A person in the early stages of dementia remains generally alert.
  • Fluctuation. The appearance of delirium symptoms can fluctuate significantly and often throughout the day. While people with dementia have better and worse times of day, their memory and thinking skills stay at a fairly constant level during the course of a day.

When to see a doctor

If a relative, friend or someone in your care shows any signs or symptoms of delirium, see a doctor. If the person has dementia, be aware of relatively sudden changes in overall awareness and engagement, which may signal delirium. Your input about the person's symptoms, as well as his or her typical thinking and everyday abilities, will be important for a diagnosis.

Older people recovering in the hospital or living in a long-term care facility are particularly at risk of delirium. Because symptoms can fluctuate and some symptoms are "quiet" — such as social withdrawal or poor responsiveness — delirium may be missed. If you notice signs and symptoms of delirium in a person in a hospital or nursing home, report your concerns to the nursing staff or doctor rather than assuming that those problems have been observed.

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

Any condition that results in a hospital stay, especially in intensive care, increases the risk of delirium. Common causes include dehydration and infections, such as urinary tract infection, pneumonia, and skin and abdominal infections. Examples of other conditions that increase the risk of delirium include:

  • Dementia
  • Older age
  • Fever and acute infection, particularly in children
  • Previous delirium episodes
  • Visual or hearing impairment
  • Poor nutrition or dehydration
  • Severe, chronic or terminal illness
  • Multiple medical problems or procedures
  • Treatment with multiple drugs
  • Alcohol or drug abuse or withdrawal

A number of medications or combinations of medications can trigger delirium, including some types of:

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

Delirium may have more than one cause, such as a medical condition and medication toxicity.

Delirium may last only a few hours or as long as several weeks or months. If factors contributing to delirium are addressed, the recovery time is often shorter.

The degree of recovery depends to some extent on the health and mental status before the onset of delirium. People with dementia, for example, may experience a significant overall decline in memory and thinking skills. People in better health are more likely to recover fully.

People with other serious, chronic or terminal illnesses may not regain the levels of thinking skills or functioning that they had before the onset of delirium. Delirium in seriously ill people is also more likely to lead to:

  • General decline in health
  • Poor recovery from surgery
  • Need for institutional care
  • Increased risk of death

The most successful approach to preventing delirium is to target risk factors that might trigger an episode. Hospital environments present a special challenge — frequent room changes, invasive procedures, loud noises, poor lighting and lack of natural light can worsen confusion.

Evidence indicates that these strategies help prevent or reduce the severity of delirium in hospitalized people:

  • Provide adequate fluids
  • Provide stimulating activities and familiar objects
  • Encourage the use of eyeglasses and hearing aids, if applicable
  • Use simple and regular communication about people, current place and time
  • Provide mobility and range-of-motion exercises
  • Reduce noise and avoid sleep interruptions
  • Provide appropriate pain management and offer nondrug treatment for sleep problems or anxiety
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