Many disorders, drugs, and poisons 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.
(See also Overview of Delirium and Dementia Overview of Delirium and Dementia Delirium and dementia are the most common causes of mental (cognitive) dysfunction—the inability to acquire, retain, and use knowledge normally. Although delirium and dementia may occur together... read more .)
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.
Although delirium and dementia Dementia Dementia is a slow, progressive decline in mental function including memory, thinking, judgment, and the ability to learn. Typically, symptoms include memory loss, problems using language and... read more both affect thinking, they are different.
Delirium affects mainly attention, and dementia affects mainly memory.
Delirium begins suddenly and often has a definite beginning point. Dementia typically begins gradually and has no definite beginning point (see table Comparing Delirium and Dementia Comparing Delirium and Dementia Delirium and dementia are the most common causes of mental (cognitive) dysfunction—the inability to acquire, retain, and use knowledge normally. Although delirium and dementia may occur together... read more ).
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.
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.
Causes of Delirium
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).
Overall, the most common causes of delirium are the following:
Drugs, particularly drugs with anticholinergic effects Anticholinergic: What Does It Mean? Drugs, the most common medical intervention, are an important part of medical care for older people. Without drugs, many older people would function less well or die at an earlier age. Older... read more , psychoactive drugs, and opioids Anticholinergic: What Does It Mean? Drugs, the most common medical intervention, are an important part of medical care for older people. Without drugs, many older people would function less well or die at an earlier age. Older... read more
Infections, such as pneumonia Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more , a bloodstream infection (sepsis Sepsis and Septic Shock Sepsis is a serious bodywide response to bacteremia or another infection plus malfunction or failure of an essential system in the body. Septic shock is life-threatening low blood pressure ... read more ), infections that affect the whole body or cause a fever, and urinary tract infections Overview of Urinary Tract Infections (UTIs) In healthy people, urine in the bladder is sterile—no bacteria or other infectious organisms are present. The tube that carries urine from the bladder out of the body (urethra) contains no bacteria... read more
Kidney failure Overview of Kidney Failure This chapter includes a new section on COVID-19 and acute kidney injury (AKI). Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney... read more , liver failure Liver Failure Liver failure is severe deterioration in liver function. Liver failure is caused by a disorder or substance that damages the liver. Most people have jaundice (yellow skin and eyes), feel tired... read more , and a low level of oxygen in the blood (hypoxia, as can occur in pneumonia), especially when these disorders begin suddenly and progress rapidly
Other causes include hospitalization, surgery, withdrawal of a drug that has been taken for a long time, certain disorders, and poisons.
Delirium can result from less severe conditions in older people and in people who have had a stroke or who have dementia Dementia Dementia is a slow, progressive decline in mental function including memory, thinking, judgment, and the ability to learn. Typically, symptoms include memory loss, problems using language and... read more , Parkinson disease Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more , or brain damage due to another condition. Less severe conditions that can trigger delirium include
Minor illnesses (such as a urinary tract infection)
Use of a bladder catheter (a thin tube used to drain urine from the bladder)
Prolonged sleep deprivation
Sensory deprivation (including being socially isolated and not having access to needed eyeglasses or hearing aids)
In some people, no cause can be identified.
Being in unfamiliar surroundings such as a hospital Confusion and Mental Decline Due to Hospitalization Being ill, particularly when it involves taking drugs for pain or anxiety, can make anyone confused. The hospital environment adds to the problem. There, people give up their personal effects... read more , 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 normal 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, and alarms. Furthermore, most people in ICUs have serious disorders and may be treated with drugs that can trigger delirium.
People in ICUs may have seizures Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more that do not cause convulsions (called nonconvulsive seizures). These seizures can cause delirium, but the seizures may not be recognized because they do not cause convulsions or other typical symptoms of seizures. If the seizures are not recognized, they may not be treated appropriately and promptly.
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.
Delirium may also develop when people who are about to have surgery do not have access to a substance they have been using, such as a recreational drug, alcohol, or tobacco. When people stop using such substances, they may have withdrawal Withdrawal Substance-induced disorders are a type of substance-related disorder that involves problems caused by the direct effects of a substance. Substance-induced disorders include Intoxication Withdrawal... read more symptoms, including delirium.
The most common reversible cause of delirium is drugs. In younger people, using illegal drugs and acute intoxication with alcohol Alcohol Alcohol (ethanol) is a depressant. Consuming large amounts rapidly or regularly can cause health problems, including organ damage, coma, and death. Genetics and personal characteristics may... read more 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:
Many other drugs can also cause delirium. The following are some examples:
Drugs with anticholinergic effects Benefits and Risks of Prescription Drugs Drugs, the most common medical intervention, are an important part of medical care for older people. Without drugs, many older people would function less well or die at an earlier age. Older... read more , including many over-the-counter (OTC) antihistamines
Amphetamines Amphetamines Amphetamines are stimulant drugs that are used to treat certain medical conditions, but are also subject to abuse. Amphetamines increase alertness, enhance physical performance, and produce... read more and cocaine Cocaine Cocaine is an addictive stimulant drug made from leaves of the coca plant. Cocaine is a strong stimulant that increases alertness, causes euphoria, and makes people feel powerful. High doses... read more , which are stimulants
Drugs that lower blood pressure (antihypertensive drugs, including beta-blockers)
Digoxin and certain other drugs used to treat heart disorders
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) or an opioid pain reliever.
Delirium commonly occurs in alcoholics who suddenly stop drinking alcohol (called delirium tremens Withdrawal symptoms Alcohol (ethanol) is a depressant. Consuming large amounts rapidly or regularly can cause health problems, including organ damage, coma, and death. Genetics and personal characteristics may... read more ) and in heroin users who suddenly stop using heroin.
Abnormal blood levels of electrolytes Overview of Electrolytes Well over half of the body's weight is made up of water. Doctors think about the body's water as being restricted to various spaces, called fluid compartments. The three main compartments are... read more , 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.
Blood sugar levels that are extremely high (hyperglycemia) or low (hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by drugs taken to control diabetes. Much less common causes of hypoglycemia include other... read more ) commonly cause delirium.
An underactive thyroid gland (hypothyroidism Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more ) causes delirium with sluggishness (lethargy). An overactive thyroid gland (hyperthyroidism Hyperthyroidism Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more ) causes delirium with hyperactivity.
If liver failure Liver Failure Liver failure is severe deterioration in liver function. Liver failure is caused by a disorder or substance that damages the liver. Most people have jaundice (yellow skin and eyes), feel tired... read more or kidney failure Overview of Kidney Failure This chapter includes a new section on COVID-19 and acute kidney injury (AKI). Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney... read more develops and is not diagnosed, a drug that a person has been taking for a long time can cause delirium, even though it previously caused no problems. In these disorders, the liver or kidneys do not process and eliminate drugs normally. As a result, drugs may accumulate in the blood and reach the brain, causing delirium.
In younger people (once drugs and alcohol are excluded), the cause of delirium is usually
A condition that directly affects the brain—for example, a brain infection, such as meningitis Introduction to Meningitis Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space). Meningitis can be... read more or encephalitis Encephalitis Encephalitis is inflammation of the brain that occurs when a virus directly infects the brain or when a virus, vaccine, or something else triggers inflammation. The spinal cord may also be involved... read more
In older people, the cause is often
A common infection, such as a urinary tract infection Overview of Urinary Tract Infections (UTIs) In healthy people, urine in the bladder is sterile—no bacteria or other infectious organisms are present. The tube that carries urine from the bladder out of the body (urethra) contains no bacteria... read more , pneumonia Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more , or influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more
Such infections can indirectly affect the brain.
Wernicke encephalopathy Wernicke Encephalopathy Wernicke encephalopathy is a brain disorder that causes confusion, eye problems, and loss of balance and results from thiamin deficiency. Wernicke encephalopathy is caused by a severe deficiency... read more , which results from by a severe deficiency of the B vitamin thiamin, can cause confusion and delirium. If untreated, Wernicke encephalopathy can cause severe brain damage, coma, or death.
Some disorders (such as strokes Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction) and symptoms that... read more , brain tumors Overview of Brain Tumors A brain tumor can be a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body... read more , or brain abscesses Abscess of the Brain A brain abscess is a pocket of pus in the brain. An abscess may form in the brain when bacteria from an infection elsewhere in the head or in the bloodstream or from a wound enter the brain... read more ) cause symptoms of delirium by directly damaging the brain.
Delirium may be the first symptom in older people with COVID-19, They may have no other symptoms of COVID-19.
Symptoms of Delirium
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 (unwarranted feelings of being persecuted) 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 Stupor and Coma Stupor is unresponsiveness from which a person can be aroused only by vigorous, physical stimulation. Coma is unresponsiveness from which a person cannot be aroused and in which the person's... read more ). Stupor may lead to coma or death.
Did You Know...
Diagnosis of Delirium
A doctor's evaluation
Mental status testing
Blood, urine, and imaging tests to check for possible causes
Doctors suspect delirium based on symptoms, particularly when people cannot pay attention and when their ability to pay attention fluctuates from one moment to the next. 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.
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 the person’s physical and mental health has been like
What drugs (including alcohol and illicit drugs, especially if the person is younger) and dietary supplements (including medicinal herbs) the person uses
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 Bipolar Disorder In bipolar disorder (formerly called manic-depressive illness), episodes of depression alternate with episodes of mania or a less severe form of mania called hypomania. Mania is characterized... read more or schizophrenia Schizophrenia Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more . People with a psychosis due to a psychiatric disorder do not have confusion or memory loss, and the level of consciousness does not change. Psychotic behavior that begins during old age usually indicates delirium or dementia.
During the physical examination, doctors check for signs of disorders that can cause delirium, such as infections and dehydration. A neurologic examination Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the nervous system. Examination of the nervous system—the... read more is also done.
Mental status testing
People who may have delirium are given a mental status test Mental Status When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the nervous system. Examination of the nervous system—the... read more . 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 mental status test also includes other questions and tasks, such as testing short-term and long-term memory, naming objects, writing sentences, and copying shapes. People with delirium may be too confused, agitated, or withdrawn to respond to this test.
Samples of blood and urine are usually taken and analyzed to check for disorders that doctors think may be causing delirium. For example, abnormalities in electrolyte and blood sugar levels and liver and kidney disorders are common causes of delirium. So doctors usually do blood tests to measure electrolyte and blood sugar levels and to evaluate how well the liver and kidneys are functioning. If doctors suspect a thyroid disorder, tests may be done to evaluate how well the thyroid gland is functioning. Or if doctors suspect that certain drugs may be the cause, they may do tests to measure drug levels in the blood. These tests can help determine whether drug levels are high enough to have harmful effects and whether a person took an overdose.
Cultures Culture of Microorganisms Infectious diseases are caused by microorganisms, such as bacteria, viruses, fungi, and parasites. Doctors suspect an infection based on the person's symptoms, physical examination results,... read more may be done to look for infections. A chest x-ray may be done to determine whether pneumonia may be the cause of delirium, especially in older people who are breathing fast, whether or not they have a fever or cough.
Computed tomography (CT) or magnetic resonance imaging (MRI) of the brain is usually done.
Sometimes a test that records the brain's electrical activity (electroencephalography Electroencephalography Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more , or EEG) is done to determine whether the delirium is caused by a seizure disorder.
Electrocardiography (ECG), pulse oximetry (using a sensor that measures oxygen levels in the blood), and a chest x-ray may be used to evaluate how well the heart and lungs are functioning.
In people with a fever or headache, a spinal tap Spinal Tap Spinal fluid is a liquid that surrounds your brain and spinal cord. Spinal fluid helps cushion your brain if you hit your head or fall. Spinal fluid moves freely around your brain and spinal... read more (lumbar puncture) 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 as possible causes.
Treatment of Delirium
Treatment of the cause
Measures to manage agitation
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.
Treatment of the cause
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 Dehydration Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration... read more , undernutrition Undernutrition Undernutrition is a deficiency of calories or of one or more essential nutrients. Undernutrition may develop because people cannot obtain or prepare food, have a disorder that makes eating or... read more , incontinence Urinary Incontinence in Adults Urinary incontinence is involuntary loss of urine. Incontinence can occur in both men and women at any age, but it is more common among women and older people, affecting about 30% of older women... read more , falls Falls in Older People Most falls occur when older people with one or more physical conditions that impair mobility or balance encounter an environmental hazard. Although many people have no symptoms before a fall... read more , and pressure sores Pressure Sores Pressure sores are areas of skin damage resulting from a lack of blood flow due to prolonged pressure. Pressure sores often result from pressure combined with pulling on the skin, friction,... read more . Preventing such problems requires meticulous care. Thus, people, particularly older people, may benefit from treatment managed by an interdisciplinary team Interdisciplinary care Providing medical care to older people can be complicated. People often have many different health care practitioners at different locations. Travel and transportation issues become more difficult... read more , which includes a doctor, physical and occupational therapists, nurses, and social workers.
Management of agitation
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.
The person's drug regimen is simplified as much as possible.
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.
Drugs are used to manage agitation only after all other measures have been ineffective. Two types of drugs are usually used to control agitation, but neither is ideal:
Antipsychotic drugs Antipsychotic drugs Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more are most often used. However, they may prolong or worsen agitation, and some have anticholinergic effects Anticholinergic: What Does It Mean? Drugs, the most common medical intervention, are an important part of medical care for older people. Without drugs, many older people would function less well or die at an earlier age. Older... read more , including confusion, blurred vision, constipation, dry mouth, light-headedness, difficulty starting and continuing to urinate, and loss of bladder control. Newer antipsychotics, such as risperidone, olanzapine, and quetiapine have fewer side effects than older antipsychotics, such as haloperidol. But if used for a long time, the newer drugs may cause weight gain and abnormal fat (lipid) levels (hyperlipidemia Dyslipidemia Dyslipidemia is a high level of lipids (cholesterol, triglycerides, or both) or a low high-density lipoprotein (HDL) cholesterol level. Lifestyle, genetics, disorders (such as low thyroid hormone... read more ) and increase the risk of type 2 diabetes Type 2 diabetes Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more . In older people with psychosis and dementia, these drugs may increase the risk of stroke, and death.
Benzodiazepines (a type of sedative Drugs Used to Treat Anxiety Disorders Anxiety is a feeling of nervousness, worry, or unease that is a normal human experience. It is also present in a wide range of psychiatric disorders, including generalized anxiety disorder,... read more ), such as lorazepam, are used when delirium is due to withdrawal from a sedative or alcohol. Benzodiazepines are not used to treat delirium caused by other conditions because they can make people, particularly older people, more confused, drowsy, or both.
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 of Delirium
Most people with delirium recover fully if the condition causing delirium is rapidly identified and treated. Any delay 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 more likely to develop complications in the hospital (including death) than those who do not have delirium. About 35 to 40% of people who have delirium while in a hospital die within 1 year, but the cause of death is often another serious disorder, not delirium itself.
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.