What Is Delirium?

Woman in hospital being helped by nurse.

David Sacks / Getty Images

Delirium, also known as acute confusional state or acute organic brain syndrome, is a medical condition that results from various causes. It involves severe confusion and rapid changes in brain function as well as a specific cluster of symptoms involving a disturbance in mental abilities and abrupt changes in the brain. It can interfere with sleep, concentration and attention, and cognitive functioning.

Delirium differs from dementia in that it develops relatively abruptly and is potentially reversible with treatment of the underlying medical condition that is causing it. Delirium can be a side effect of certain medications, medical conditions, or have other causes such as alcohol withdrawal or surgery.


In general, delirium involves fluctuations in mental states, states of confusion, and issues with typical cognitive functions.Typical symptoms include:

  • Reduced perceptional and sensory abilities
  • Abrupt changes in movement (hyperactivity or slowness)
  • Sleep cycle changes (sleeping more, drowsiness)
  • Confusion about whereabouts and time
  • Lack of concentration (easily distracted)
  • Inability to recall recent memories
  • Trouble speaking and organizing thoughts (rambling, nonsense speech)
  • Personality changes (mood swings, irritability, anger, fear, paranoia)
  • Incontinence
  • Trouble writing or reading
  • Apathy
  • Calling out or moaning
  • Hallucinations
  • Withdrawal

Delirium usually starts quickly, within a period of hours or days. In a hospital setting, it might last a week or longer and can progress to a coma or death if not properly treated.

Symptoms generally fluctuate throughout the day, with some periods of no symptoms. Delirium tends to be worse at night when the environment does not look as familiar.

Diagnostic Criteria

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) lists the following five criteria for a diagnosis of delirium:

  1. There is a disturbance in attention and awareness.
  2. The disturbance develops over a short period of time, generally within hours or days. There is a change from normal attention and awareness and this change fluctuates throughout the day.
  3. In addition, there is a disturbance in cognition in another way, in terms of language, memory, orientation (time and space), or perception.
  4. The disturbances are not better explained by a pre-existing, evolving, or established neurocognitive disorder. The patient also cannot be in a state of low arousal (i.e., coma).
  5. There must be evidence that the delirium is due to the direct physiological outcome of a medical condition, substance intoxication/withdrawal, exposure to a toxin, or resulting from multiple etiologies.

Delirium vs. Dementia

While delirium and dementia might seem hard to tell apart on the surface, and the fact that a person can be experiencing both delirium and dementia at the same time (delirium happens often in people with dementia), there are key differences:

Delirium Is Not Always a Sign of Dementia

Having delirium does not mean that a person is living with dementia. Dementia involves the progressive decline of thinking skills and memory due to a loss of brain cells and brain dysfunction. The most common cause of dementia is Alzheimer's disease.

Delirium Has a Quick Onset

Delirium comes on abruptly in those who are experiencing it. Attention becomes very impaired with delirium, whereas a person with early dementia will generally not have fluctuating alertness. Additionally, dementia is a fairly constant state overall, whereas delirium tends to fluctuate throughout the day.

Types of Delirium

There are actually three main types as well as delirium tremens which is related to alcoholism.

Hyperactive Delirium

This type of delirium tends to involve restlessness, agitation, rapid mood swings or hallucinations. It may result in a patient refusing to cooperate with a caregiver.

Hypoactive Delirium

This type of delirium tends to involve reduced activity, being sluggish, becoming drowsy, or appearing to be in a daze. Persons with this type of delirium will often sleep more and may miss some meals.

Mixed Delirium

The mixed delirium type involves symptoms of both hyperactive and hypoactive delirium. A person with this type of delirium may switch back and forth between the two different states of hyperactive delirium and hypoactive delirium.

Delirium Tremens

Delirium tremens is a severe form of delirium that results from withdrawal from alcohol consumption among persons who have been drinking large amounts of alcohol for a long period.


Delirium is usually the result of an underlying physical illness that causes impaired signaling in the brain. Delirium can have one single cause or multiple causes. Below is a list of some of the specific potential causes of delirium:

  • Oxygen deprivation (e.g., due to asthma)
  • Toxins in the brain (e.g., exposure to carbon monoxide, cyanide poisoning)
  • Alcohol or drug abuse (overdose, withdrawal)
  • Acute infections (e.g., urinary tract infection)
  • Severe lack of sleep or sleep deprivation
  • General anesthesia
  • Inflammatory diseases
  • Medication (a variety of medications can contribute to delirium)
  • Metabolic imbalance or electrolyte disturbance (e.g., low sodium)
  • Fever
  • Malnutrition or dehydration
  • Stroke, heart attack, or a severe injury

Risk Factors

There are several risk factors for delirium. Below is a list of some of the most common risk factors:

  • Hospital stays, particularly in the intensive care unit (ICU) or after surgery, involving frequent room changes, multiple procedures, loud noises, or poor lighting
  • Living in a nursing home
  • Being an older adult
  • Lack of sleep
  • Living with dementia or Parkinson's disease
  • Previous episodes of delirium
  • Having a hearing or vision impairment
  • Being aged over 65
  • Having multiple medical conditions


In general, when the issues that cause the delirium are addressed, the recovery period will be shorter. The degree of recovery also depends on the general health status of the person prior to developing delirium. In other words, a person's mental status before delirium plays a role. Those in better health prior to developing delirium will be more likely to fully recover in a shorter period of time.

In those with serious illnesses, delirium may lead to the following complications:

  • A general decline in health
  • Poor recovery from surgery
  • The need for care in an institution
  • Loss of ability to care for oneself
  • Loss of ability to interact with others
  • Progression to coma, stupor, and increased risk of death

Prevention of Delirium in Hospital Patients

The best way to prevent delirium is to be aware of the risk factors and mitigate them through proactive measures such as the following:

  • Promote good sleep by reducing noise and distractions
  • Help hospital patients stay oriented to time and space
  • Avoid unnecessary medical procedures
  • Avoid the use of sedatives


Below are some of the physical examinations and tests that might be done when conducting an assessment for delirium:

  • Blood chemistry tests
  • Head scans (CT, MRI)
  • Drug and alcohol testing
  • Thyroid testing
  • Chest x-ray
  • Electroencephalogram (EEG)

In addition, a mental status test would be conducted. For example, the Confusion Assessment Method involves observing whether a patient can speak, think, and move normally and whether their behavior changes throughout the day.


Treatment depends on the cause of the delirium. If a person is not already hospitalized, a hospital stay may become necessary.

Certain medications will need to be stopped (e.g., central nervous system depressants, analgesics, anticholinergics), and the use of any alcohol or drugs must be discontinued.

Finally, basic assistive devices such as eyeglasses or hearing aids may help those with impairments.

Medications for Delirium

Medications may be given to manage the underlying cause of delirium. Below are some examples.

  • Inhaler/breathing machine for severe asthma
  • Antibiotics for bacterial infections
  • Antidepressants for depression or agitation
  • Sedatives for alcohol withdrawal
  • High potency antipsychotics to manage agitation


    Full recovery from delirium is possible depending on the underlying cause and how well it is treated. It may take a patient several weeks to fully recover from delirium.

    When to See a Doctor

    How do you know if your loved one should be seen by a doctor? Or what do you do if your loved one is already in the hospital and you are concerned that they may be experiencing delirium?

    Older People Are More At Risk

    First, recognize that older people enduring hospital stays are most at risk for delirium. If your loved one is in the hospital and showing the signs and symptoms listed above, it's important not to assume that the hospital staff or medical staff have noticed this change.

    Record Behavioral Changes

    You will need to tell doctors about the changes that you are seeing from normal functioning and how you see a someone acting differently. It may help for you to keep a record or log of events as they happen so that you can explain what you are seeing and also how it changes over time. A record of your observations will allow the hospital staff to intervene as necessary.

    Schedule Appointments

    If, on the other hand, you have a loved one or relative who is not in the hospital and is showing signs of delirium, it is important to help that person visit the doctor for an assessment or, if symptoms are severe, you may need to take them to the emergency department for immediate help.

    A Word From Verywell

    Delirium is a treatable acute condition that is most common among older individuals and those who have been hospitalized. The best thing you can do is to familiarize yourself with the signs and symptoms of delirium so that you can be aware of what to look for when visiting loved ones who are older or in the hospital.

    While it may be scary to experience delirium or to witness someone else experiencing it, know that a full recovery is possible with appropriate treatment. For this reason, it's best that delirium is caught as early as possible. If you notice the signs and symptoms in a loved one, it's better to act on them quickly rather than to let the situation extend. The longer your loved one experiences symptoms, the more time it will take for them to make a full recovery.

    3 Sources
    Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
    1. Psychology Today. Delirium.

    2. Setters B, Solberg LM. Delirium. Prim Care. 2017;44(3):541-559.

    3. Inouye SK, Westendorp RGJ, Saczynski JS. Delirium in elderly people. Lancet. 2014;383(9920):911-922.

    By Arlin Cuncic, MA
    Arlin Cuncic, MA, is the author of "Therapy in Focus: What to Expect from CBT for Social Anxiety Disorder" and "7 Weeks to Reduce Anxiety." She has a Master's degree in psychology.