Delirium is a sudden, fluctuating, and usually reversible disturbance of mental function. It is characterized by inability to pay attention, disorientation, an inability to think clearly, and fluctuations in the level of alertness (consciousness).

• Many disorders and drugs can cause delirium.
• Doctors base the diagnosis on symptoms and results of a physical examination, and they use blood, urine, and imaging tests to identify the cause.
• Promptly correcting or treating the condition causing delirium usually cures it.

Delirium is an abnormal mental state, not a disease. Although the term has a specific medical definition, it is often used to describe any type of confusion. Delirium is never normal and often indicates a usually serious, newly developed problem, especially in older people. People who have delirium need immediate medical attention. If the cause of delirium is identified and corrected quickly, delirium can usually be cured.

Because delirium is a temporary condition, determining how many people have it is difficult. Delirium affects 15 to 50% of hospitalized people aged 70 or older.

Delirium may occur at any age but is more common among older people. Delirium is common among residents of nursing homes. When delirium occurs in younger people, it is usually due to drug use or a life-threatening disorder.

What Is Confusion?
Confusion means different things to different people, but doctors use the term to describe people who cannot process information normally. Confused people cannot Follow a conversation Answer questions appropriately Understand where they are Make critical judgments that affect safety Remember important facts Confusion has many different causes, including the use of certain drugs (prescription, over-the-counter, and illegal) and a wide variety of disorders. Delirium and dementia, though very different disorders, both cause confusion. When a person is confused, doctors try to determine what the cause is, particularly whether it is delirium or dementia. If confusion develops or worsens suddenly, the cause may be delirium. In such cases, medical attention is needed immediately because delirium may be caused by a serious disorder. Also, treating the cause, once identified, can often reverse the delirium. If confusion develops slowly, the cause may be dementia. Medical attention is needed but not urgently. Treatment may slow the mental decline in people with dementia but usually cannot stop the decline.

Causes

Development or worsening of many disorders can cause delirium. Any person can become delirious when extremely ill or taking drugs that affect brain function (psychoactive drugs). However, delirium can result from less severe conditions in older people and in people who have had a stroke or who have dementia, Parkinson's disease, or another disorder that causes nerve degeneration. In such people, delirium can result from a relatively minor illness (such as a urinary tract infection), dehydration, sensory deprivation (including being socially isolated or not having access to needed eyeglasses or hearing aids), or prolonged sleep deprivation. In some people, no cause can be identified.

Hospitalization: Being in the hospital, particularly in an intensive care unit (ICU), can contribute to or trigger delirium. In ICUs, people are isolated in a room that typically has no windows or clocks. Thus, people are deprived of sensory stimulation and can become disoriented. Sleep is disturbed by staff members who awaken people during the night to monitor and treat them and by loud beeping monitors, intercoms, voices in the hallway, or alarms. Furthermore, most people in ICUs have serious disorders and are treated with drugs, which can make delirium even more likely. The delirium that may result is sometimes called ICU psychosis.

Surgery: Delirium is also very common after surgery, probably because of the stress of surgery, the anesthetics used during surgery, and the pain relievers (analgesics) used after surgery.

Drugs: The most common reversible cause of delirium is drugs. In younger people, use of illegal drugs and acute intoxication with alcohol are common causes. In older people, prescription drugs are usually the cause.

Psychoactive drugs directly affect nerve cells in the brain, sometimes causing delirium. They include the following:

• Opioids (including morphine and meperidine)
• Sedatives (including benzodiazepines and sleep aids)
• Antipsychotics
• Antidepressants

Many other drugs can also cause delirium. The following are some examples:

• Drugs with anticholinergic effects (see Aging and Drugs: Anticholinergic: What Does It Mean?), including many over-the-counter (OTC) antihistamines
• Amphetamines and cocaine, which are stimulants
• Cimetidine
• Corticosteroids
• Digoxin
• Levodopa
• Muscle relaxants

Delirium can also result from suddenly stopping a drug that has been taken for a long time—for example, a sedative (such as a benzodiazepine or barbiturate). Delirium commonly occurs in alcoholics who suddenly stop drinking alcohol (see Drug Use and Abuse: Withdrawal Symptoms) and in heroin users who suddenly stop using heroin.

Disorders: Abnormal blood levels of electrolytes, such as calcium, sodium, or magnesium, can interfere with the metabolic activity of nerve cells and lead to delirium. Abnormal electrolyte levels may result from use of a diuretic, dehydration, or disorders such as kidney failure and widespread cancer. An underactive thyroid gland (hypothyroidism) causes delirium with lethargy. An overactive thyroid gland (hyperthyroidism) causes delirium with hyperactivity.

In younger people, the cause of delirium is usually a condition that directly affects the brain—for example a brain infection, such as meningitis or encephalitis. In older people, the cause is usually a disorder that affects other parts of the body, such as a urinary tract infection, pneumonia, or influenza. Such infections can indirectly affect the brain.

Poisons: In younger people, ingestion of poisons, such as rubbing alcohol or antifreeze, is a common cause of delirium.

Spotlight on Aging
Delirium is more common among older people. It is a common reason that family members of older people seek help from a doctor or at a hospital. About 15 to 50% of older people experience delirium at some time during a hospital stay. In older people, delirium can result from any condition that causes delirium in younger people. But it can also result from less severe conditions, such as the following: Dehydration A disorder that normally does not affect thinking, such as a urinary tract infection, influenza, or deficiency of thiamin or vitamin B12 Retention of urine or feces Sensory deprivation, as may occur when people are socially isolated or are not wearing their glasses or hearing aid Sleep deprivation Stress (any type) Older people are much more sensitive to many drugs. In older people, drugs that affect the way the brain functions, such as sedatives, are the most common cause of delirium. However, drugs that do not affect brain function, including many over-the-counter drugs (especially antihistamines), can also cause it. Older people are more sensitive to the anticholinergic effects that many of these drugs have. One of these effects is confusion. Why delirium occurs more often in older people is not known. One possible explanation involves acetylcholine, a neurotransmitter (a substance that enables brain cells to communicate with each other). Any stress (due to a drug, disorder, or situation) causes the level of acetylcholine to decrease, interfering with the brain's functioning. As people age, the brain produces less acetylcholine. Thus, if any condition causes the acetylcholine level to decrease further in older people, they are more likely to experience delirium. Older people are also more likely to have other conditions that make them more susceptible to delirium, such as the following: Stroke Dementia Parkinson's disease Other disorders that cause nerve degeneration Use of three or more drugs Dehydration Undernutrition Immobility Delirium tends to last longer in older people. It is often the first sign of another, sometimes serious disorder. Confusion, the most obvious symptom, may be harder to recognize in older people. Younger people with delirium may be agitated, but very old people tend to become quiet and withdrawn. In such cases, recognizing delirium is even harder. If a psychosis develops in older people, it usually indicates delirium or dementia. Psychosis due to a psychiatric disorder rarely begins during old age. Older people are more likely to have dementia, which makes delirium harder to identify. Both cause confusion. Doctors try to distinguish the two by determining how quickly the confusion developed and what the person's previous mental function was. Doctors also ask the person a series of questions that test various aspects of thinking (mental status examination). Doctors usually treat people whose mental function suddenly worsens—even if they have dementia—as if they have delirium until proved otherwise. Delirium and the hospitalization it usually requires can cause many other problems, such as undernutrition, dehydration, and pressure sores, which may have serious consequences in older people. Thus, older people can benefit from treatment managed by an interdisciplinary team, which includes a doctor, physical and occupational therapists, nurses, and social workers. To help prevent delirium in an older person during a hospital stay, family members can ask hospital staff members to help—by encouraging the person to move around regularly, by placing a clock and calendar in the room, by minimizing the interruptions and noises during the night, and by making sure the person eats and drinks enough. Family members can visit and talk with the person and thus help keep the person oriented.

Symptoms

Delirium usually begins suddenly and progresses over hours or days. The actions of people with delirium vary but roughly resemble those of a person who is becoming progressively more intoxicated.

The hallmark of delirium is an inability to pay attention. People with delirium cannot concentrate, so they have trouble processing new information and cannot recall recent events. Thus, they do not understand what is happening around them. They become disoriented. Sudden confusion about time and often about place (where they are) may be an early sign of delirium. If delirium is severe, people may not know who they or other people are. Thinking is confused, and people with delirium ramble, sometimes becoming incoherent. Their level of awareness (consciousness) may fluctuate. That is, people may be overly alert one moment and drowsy and sluggish the next. Other symptoms also often change within minutes and tend to worsen during the evening (a phenomenon called sundowning). People with delirium often sleep restlessly or reverse their sleep-wake cycle, sleeping during the day and staying awake at night.

People may have bizarre, frightening visual hallucinations, seeing things or people that are not there. Some people develop paranoia or have delusions (false beliefs usually involving a misinterpretation of perceptions or experiences).

Personality and mood may change. Some people become so quiet and withdrawn that no one notices that they are delirious. Others become irritable, agitated, and restless and may pace. People who develop delirium after taking sedatives are likely to become very drowsy and withdrawn. Those who have taken amphetamines or who have stopped taking sedatives may become aggressive and hyperactive. Some people alternate between the two types of behavior.

Delirium can last hours, days, or even longer, depending on the severity and the cause. If the cause of delirium is not quickly identified and treated, people may become increasingly drowsy and unresponsive, requiring vigorous stimulation to be aroused (a condition called stupor—see Coma and Impaired Consciousness: Stupor and Coma). Stupor may lead to coma or death.

Did You Know... A psychosis that begins during old age usually indicates delirium or dementia.

Diagnosis

Doctors suspect delirium based on symptoms. However, mild delirium may be difficult to recognize. Doctors may not recognize delirium in hospitalized people.

Most people thought to have delirium are hospitalized to evaluate them and protect them from injuring themselves or others. Diagnostic procedures can be done quickly and safely in the hospital, and any disorders detected can be treated quickly.

Because delirium may be caused by a serious disorder (which could be rapidly fatal), doctors try to identify the cause as quickly as possible. Treating the cause, once identified, can often reverse the delirium.

Doctors first try to distinguish delirium from other disorders that affect mental function. Doctors do so by collecting as much information about the person's medical history as possible, by doing a physical examination, and by testing.

Medical History: Friends, family members, or other observers are asked for information because people with delirium are usually unable to answer. Questions include the following:

• How the confusion began (suddenly or gradually)
• How quickly it progressed
• What has the person's physical and mental health been like
• What drugs (including alcohol and illicit drugs, especially if the person is younger) and dietary supplements does the person use
• Whether any drugs have been started or stopped recently

Information may also come from medical records, the police, emergency medical personnel, or evidence such as pill bottles and certain documents. Documents such as a checkbook, recent letters, or notification of unpaid bills or missed appointments can indicate a change in mental function.

If delirium is accompanied by agitation and hallucinations, delusions, or paranoia, it must be distinguished from a psychosis due to a psychiatric disorder, such as manic-depressive illness or schizophrenia. People with a psychosis due to a psychiatric disorder do not have confusion or memory loss, and the level of consciousness does not change. A psychosis that begins during old age usually indicates delirium or dementia.

Physical Examination: During the physical examination, doctors check for signs of disorders that can cause delirium, such as infections and dehydration. A neurologic examination is also done (see Symptoms and Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Physical Examination). People who may have delirium are given a mental status test. First, they are asked questions to determine whether the main problem is being unable to pay attention. For example, they are read a short list and asked to repeat it. Doctors must determine whether people take in (register) what is read to them. People with delirium cannot. The test also includes other questions and tasks, such as testing short-term and long-term memory, naming objects, writing sentences, and copying shapes.

Testing: Samples of blood and urine are taken and analyzed. Cultures are done to look for signs of infection. Computed tomography (CT) or magnetic resonance imaging (MRI) are usually done. Electrocardiography, pulse oximetry (using a sensor that measures oxygen levels in the blood), and a chest x-ray may be used to evaluate heart and lung function.

In people with a fever or headache, a spinal tap (lumbar puncture—see Symptoms and Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Tests for Brain, Spinal Cord, and Nerve Disorders) may be done to obtain cerebrospinal fluid for analysis. Such analysis helps doctors rule out infection of or bleeding around the brain and spinal cord.

PrintOpen table in new window
Delirium or Psychosis? Feature Delirium Psychosis Due to a Psychiatric Disorder Orientation Confused about current time, date, place, or identity Usually, aware of time, date, place, and identity Attention Greatly impaired Unaffected Memory for recent events Lost Retained Ability to calculate Unable to do simple calculations Retained Hallucinations If present, mostly visual or involving touch If present, mostly auditory Other disorders Often present and may be serious History of previous psychiatric disturbances Drug use Often, evidence of recent drug use Not necessarily involved

Treatment

Most people who have delirium are hospitalized. However, when the cause of delirium can be corrected readily (for example, when the cause is low blood sugar), people are observed for a short time in the emergency department and can then return home.

Once the cause is identified, it is promptly corrected or treated. For example, doctors treat infections with antibiotics, dehydration with fluids and electrolytes given intravenously, and delirium due to stopping alcohol with benzodiazepines (as well as measures to help people not start drinking alcohol again). Prompt treatment of the disorder causing delirium usually prevents permanent brain damage and may result in a complete recovery. Any drugs that may be making the delirium worse are stopped if possible.

General measures are also important. The environment is kept as quiet and calm as possible. It should be well-lit to enable people to recognize what and who is in their room and where they are. Placing clocks, calendars, and family photographs in the room can help with orientation. At every opportunity, staff and family members should reassure people and remind them of the time and place. Procedures should be explained before and as they are done. People who need glasses or hearing aids should have access to them.

People who have delirium are prone to many problems, including dehydration, undernutrition, incontinence, falls, and pressure sores. Preventing such problems requires meticulous care. Thus, people, particularly older people, may benefit from treatment managed by an interdisciplinary team, which includes a doctor, physical and occupational therapists, nurses, and social workers.

People who are extremely agitated or who have hallucinations may injure themselves or their caregivers. The following measures can help prevent such injuries:

• Family members are encouraged to stay with the person.
• The person is put in a room near the nurses' station.
• The hospital may provide an attendant to stay with the person.
• Devices, such as intravenous lines, bladder catheters, or padded restraints, are not used if possible because they can further confuse and upset the person, increasing the risk of injury.

However, sometimes during hospitalization, padded restraints must be used—for example, to keep the person from pulling out intravenous lines and to prevent falls. Restraints are applied carefully by a staff member trained in their use, released at frequent intervals, and stopped as soon as possible, because they can upset the person and worsen agitation.

For agitation, drugs are used only after all other measures have been ineffective. Two types of drugs are usually used to control agitation, but neither is ideal:

• Antipsychotic drugs (see Schizophrenia and Delusional Disorder: Antipsychotic Drugs) are most often used. However, they may prolong or worsen agitation. Newer antipsychotics, such as risperidone, are less likely to worsen agitation and have fewer side effects than older antipsychotics, such as haloperidol. But if used for a long time in people with dementia, the newer drugs may increase the risk of stroke and death.
• Benzodiazepines (a type of sedative—see Anxiety Disorders: Generalized Anxiety Disorder and Anxiety Disorders: Drugs Used to Treat Anxiety Disorders), such as lorazepam, usually calm people with delirium but make some people, particularly older people, more confused, drowsy, or both. Benzodiazepines are preferred when delirium is due to suddenly stopping sedatives or alcohol after heavy use for a long time. Benzodiazepines have more side effects than antipsychotics.

Doctors are careful when prescribing these drugs, particularly for older people. They use the lowest dose possible and stop the drug as soon as possible.

Prognosis

Most people recover fully if the condition causing delirium is rapidly identified and treated. Any delay greatly decreases the chance of a full recovery. Even when delirium is treated, some symptoms may persist for many weeks or months, and improvement may occur slowly. In some people, delirium evolves into chronic brain dysfunction similar to dementia.

Hospitalized people who have delirium are up to 10 times more likely to develop complications in the hospital (including death) than those who do not have delirium. Hospitalized people who have delirium, particularly older people, have a longer hospital stay, higher treatment costs, and a longer recovery time after they leave the hospital.

Last full review/revision February 2008 by Juebin Huang, MD, PhD