Delirium is a serious change in mental abilities. It results in confused thinking and a lack of awareness of someone's surroundings. The disorder usually comes on fast — within hours or a few days.

Delirium can often be traced to one or more factors. Factors may include a severe or long illness or an imbalance in the body, such as low sodium. The disorder also may be caused by certain medicines, infection, surgery, or alcohol or drug use or withdrawal.

Symptoms of delirium are sometimes confused with symptoms of dementia. Health care providers may rely on input from a family member or caregiver to diagnose the disorder.


Symptoms of delirium usually begin over a few hours or a few days. They typically occur with a medical problem. Symptoms often come and go during the day. There may be periods of no symptoms. Symptoms tend to be worse at night when it's dark and things look less familiar. They also tend to be worse in settings that aren't familiar, such as in a hospital.

Primary symptoms include the following.

Reduced awareness of surroundings

This may result in:

  • Trouble focusing on a topic or changing topics
  • Getting stuck on an idea rather than responding to questions
  • Being easily distracted
  • Being withdrawn, with little or no activity or little response to surroundings

Poor thinking skills

This may appear as:

  • Poor memory, such as forgetting recent events
  • Not knowing where they are or who they are
  • Trouble with speech or recalling words
  • Rambling or nonsense speech
  • Trouble understanding speech
  • Trouble reading or writing

Behavior and emotional changes

These may include:

  • Anxiety, fear or distrust of others
  • Depression
  • A short temper or anger
  • A sense of feeling elated
  • Lack of interest and emotion
  • Quick changes in mood
  • Personality changes
  • Seeing things that others don't see
  • Being restless, anxious or combative
  • Calling out, moaning or making other sounds
  • Being quiet and withdrawn — especially in older adults
  • Slowed movement or being sluggish
  • Changes in sleep habits
  • A switched night-day sleep-wake cycle

Types of delirium

Experts have identified three types:

  • Hyperactive delirium. This may be the easiest type to recognize. People with this type may be restless and pace the room. They also may be anxious, have rapid mood swings or see things that aren't there. People with this type often resist care.
  • Hypoactive delirium. People with this type may be inactive or have reduced activity. They tend to be sluggish or drowsy. They might seem to be in a daze. They don't interact with family or others.
  • Mixed delirium. Symptoms involve both types of delirium. The person may quickly switch back and forth from being restless and sluggish.

Delirium and dementia

Delirium and dementia may be hard to tell apart, and a person may have both. Someone with dementia has a gradual decline of memory and other thinking skills due to damage or loss of brain cells. The most common cause of dementia is Alzheimer's disease, which comes on slowly over months or years.

Delirium often occurs in people with dementia. However, episodes of delirium don't always mean a person has dementia. Tests for dementia shouldn't be done during a delirium episode because the results could be misleading.

Some differences between the symptoms of delirium and dementia include:

  • Onset. The onset of delirium occurs within a short time — within a day or two. Dementia usually begins with minor symptoms that get worse over time.
  • Attention. The ability to stay focused or maintain focus is impaired with delirium. A person in the early stages of dementia remains generally alert. Someone with dementia often isn't sluggish or agitated.
  • Rapid changes in symptoms. Delirium symptoms can come and go several times during the day. While people with dementia have better and worse times of day, their memory and thinking skills typically stay at a constant level.

When to see a doctor

If a relative, friend or someone in your care shows symptoms of delirium, talk to the person's health care provider. Your input about symptoms, typical thinking and usual abilities will be important for a diagnosis. It also can help the provider find the cause of the disorder.

If you notice symptoms in someone in the hospital or nursing home, report your concerns to the nursing staff or health care provider. The symptoms may not have been observed. Older people who are in the hospital or are living in a long-term care center are at risk of delirium.

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Delirium occurs when signals in the brain aren't sent and received properly.

The disorder may have a single cause or more than one cause. For example, a medical condition combined with the side effects of a medicine could cause delirium. Sometimes no cause can be found. Possible causes include:

  • Certain medicines or medicine side effects
  • Alcohol or drug use or withdrawal
  • A medical condition such as a stroke, heart attack, worsening lung or liver disease, or an injury from a fall
  • An imbalance in the body, such as low sodium or low calcium
  • Severe, long-lasting illness or an illness that will lead to death
  • Fever and a new infection, particularly in children
  • Urinary tract infection, pneumonia, the flu or COVID-19, especially in older adults
  • Exposure to a toxin, such as carbon monoxide, cyanide or other poisons
  • Poor nutrition or a loss of too much body fluid
  • Lack of sleep or severe emotional distress
  • Pain
  • Surgery or another medical procedure that requires being put in a sleep-like state

Some medicines taken alone or taken in combination can trigger delirium. These include medicines that treat:

  • Pain
  • Sleep problems
  • Mood disorders, such as anxiety and depression
  • Allergies
  • Asthma
  • Swelling
  • Parkinson's disease
  • Spasms or convulsions

Risk factors

Any condition that results in a hospital stay increases the risk of delirium. This is mostly true when someone is recovering from surgery or is put in intensive care. Delirium is more common in older adults and in people who live in nursing homes.

Examples of other conditions that may increase the risk of delirium include:

  • Brain disorders such as dementia, stroke or Parkinson's disease
  • Past delirium episodes
  • Vision or hearing loss
  • Multiple medical problems


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

Recovery depends to some extent on the health and mental status before symptoms began. People with dementia, for example, may experience an overall decline in memory and thinking skills after a delirium episode. People in better health are more likely to fully recover.

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

  • A general decline in health
  • Poor recovery from surgery
  • The need for long-term care
  • An increased risk of death


The best way to prevent delirium is to target risk factors that might trigger an episode. Hospital settings present a special challenge. Hospital stays often involve room changes, invasive procedures, loud noises and poor lighting. Lack of natural light and lack of sleep can make confusion worse.

Some steps can help prevent or reduce the severity of delirium. To do this, promote good sleep habits, help the person remain calm and well-oriented, and help prevent medical problems or other complications. Also avoid medicines used for sleep, such as diphenhydramine (Benadryl Allergy, Unisom, others).

Oct. 14, 2022
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