Delirium is a medical condition characterized by a vascillating general disorientation, which is accompanied by cognitive impairment, mood shift, self-awareness, and inability to attend (the inability to focus and maintain attention). The change occurs over a short period of time— hours to days— and the disturbance in consciousness fluctuates throughout the day.


The word delirium comes from the Latin delirare . In its Latin form, the word means to become crazy or to rave. A phrase often used to describe delirium is "clouding of consciousness," meaning the person has a diminished awareness of their surroundings. While the delirium is active, the person tends to fade into and out of lucidity, meaning that he or she will sometimes appear to know what's going on, and at other times, may show disorientation to time, place, person, or situation. It appears that the longer the delirium goes untreated, the more progressive the disorientation becomes. It usually begins with disorientation to time, during which a patient will declare it to be morning, even though it may be late night. Later, the person may state that he or she is in a different place rather than at home or in a hospital bed. Still later, the patient may not recognize loved ones, close friends, or relatives, or may insist that a visitor is someone else altogether. Finally, the patient may not recognize the reason for his/her hospitalization and might accuse staff or others of some covert reason for his/her hospitalization (see example below). In fact, this waxing and waning of consciousness is often worse at the end of a day, a phenomenon known as "sundowning."

A delirious patient will have a difficult time with most mental operations. Due to the fact that the patient is unable to attend consistently to his environment, he/she can become disoriented. Nevertheless, disorientation and memory loss are not essential to the diagnosis of delirium; the inability to focus and maintain attention, however, is essential to rendering a correct diagnosis. Left unchecked, delirium tends to transition from inattention to increased levels of lethargy, leading to torpor, stupor, and coma. In its other form, delirious patients become agitated and almost hypervigilant, with their sleep-wake cycle dramatically altered, fluctuating between great guardedness and hypersomnia (excessive drowsiness) during the day and wakefulness during the night. Delirious patients can also experience hallucinations of the visual, auditory, or tactile type. In such cases, the patient will see things others cannot see, hear things others cannot hear, and/or feel things that others cannot, such as feeling as though his or her skin is crawling. In short, the extremes of delirium range from the appearance of simple confusion and apathy to the anxious, agitated, and hyperactive type, with some patients experiencing both ends of the spectrum during a single episode. It is imperative that a quick evaluation occur if delirium is suspected, because it can lead to death.

Causes and symptoms


While the symptoms of delirium are numerous and varied, the causes of delirium fall into four basic categories: metabolic, toxic, structural, and infectious. Stated another way, the bases of delirium may be medical, chemical, surgical, or neurological. Many metabolic disorders, such as hypothyroidism, hyperthyroidism, hypokalemia, anoxia, etc. can cause delirium. For example, hypothyroidism (the thyroid gland emits reduced levels of thyroid hormones) brings about a change in emotional responsiveness, which can appear similar to depressive symptoms and cause a state of delirium. Other metabolic sources of delirium involve the dysfunction of the pituitary gland, pancreas, adrenal glands, and parathyroid glands. It should be noted that when a metabolic imbalance goes unattended, the brain may suffer irreparable damage.

One of the most frequent causes of delirium in the elderly is overmedication. The use of medications such as tricyclic antidepressants and antiparkinsonian medications can bring about an anticholinergic toxicity and subsequent delirium. In addition to the anticholinergic drugs, other drugs that can be the source of a delirium are:

  • anticonvulsants, used to treat epilepsy
  • antihypertensives, used to treat high blood pressure
  • cardiac glycosides, such as Digoxin, used to treat heart failure
  • cimetidine, used to reduce the production of stomach acid disulfiram , used in the treatment of alcoholism
  • insulin, used to treat diabetes
  • opiates, used to treat pain
  • phencyclidine (PCP), used originally as an anesthetic, but later removed from the market, now only produced and used illicitly
  • salicylates, basically found in aspirin
  • steroids, sometimes used to prevent muscle wasting in bedridden or other immobile patients

Additionally, systemic poisoning by chemicals or compounds such as carbon monoxide, lead, mercury, or other industrial chemicals can be the source of delirium.

Just as the ingestion of certain drugs may cause delirium in some patients, the withdrawal of drugs can also cause it. Alcohol is the most widely used and most well known of these drugs whose withdrawal symptoms may include delirium. Delirium onset from the abstinence of alcohol in a chronic user can begin within three days of cessation of drinking. The term delirium tremens is used to describe this form of delirium. The resulting symptoms of this delirium are similar in nature to other delirious states, but may be preceded by clear-headed auditory hallucinations. In other words, the delirium has not begun, but the patient may experience auditory hallucinations. Delirium tremens follow and can have ominous consequences with as many as 15% dying.

Some of the structural causes of delirium include vascular blockage, subdural hematoma, and brain tumors. Any of these can damage the brain, through oxygen deprivation or direct insult, and cause delirium. Some patients become delirious following surgery. This can be due to any of several factors, such as: effects of anesthesia, infections, or a metabolic imbalance.

Infectious diseases can also cause delirium. Commonly diagnosed diseases such as urinary tract infections, pneumonia, or fever from a viral infection can induce delirium. Additionally, diseases of the liver, kidney, lungs, and cardiovascular system can cause delirium. Finally, an infection, specific to the brain, can cause delirium. Even a deficiency of thiamin (vitamin B1) can be a trigger for delirium.


Symptoms of delirium include a confused state of mind accompanied by poor attention, impaired recent memory, irritability, inappropriate behavior (such as the use of vulgar language, despite lack of a history of such behavior), and anxiety and fearfulness. In some cases, the person can appear to be psychotic, fostering illusions, delusions , hallucinations, and/or paranoia . In other cases, the patient may simply appear to be withdrawn and apathetic. In still other cases, the patient may become agitated and restless, unable to remain in bed, and feel a strong need to pace the floor.

A few examples of people affected by delirium follow:

  • One gentleman, who had already been in the hospital for three days, when asked if he knew where he was, stated the correct city and hospital. He immediately followed this by saying, "but I started out in Dallas, Texas this morning." The hospital location was some 1,800 miles from Dallas, Texas, and as previously indicated, he had been in the same hospital for three days.
  • In another case, an elderly gentleman was placed in a private room that had a wonderful large mural on one wall. The mural was that of a forest scene—no animals or people, only trees and sunlight. His chief complaint at various points during the day was that evil people were watching him from behind the trees in the forest scene.
  • An elderly woman had to be subdued while attempting to flee from the hospital, because she was convinced that she had been brought there so surgeons could harvest her organs. Despite the lack of surgical scars or incisions, she insisted that she had been taken to the basement of the hospital the previous night and a surgeon had removed one of her kidneys.


Delirium occurs most frequently in the elderly and the young, but can occur in anyone at any age. Of persons over 65 who are brought to the hospital for a general medical condition, roughly 10% show signs of delirium at admission. It is suspected that another 10%-15% may develop delirium while in the hospital. There appears to be no gender difference—delirium seems to affect males and females equally.


Whether or not delirium is diagnosed in a patient depends on the type manifest. If the case is an elderly, postoperative patient who appears quiet and apathetic, the condition may go undiagnosed. However, if the patient presents with the agitated, uncooperative type of delirium, it will certainly be noticed. In any case, where there is sudden onset of a confused state accompanied by a behavioral change, delirium should be considered. This is not intended to imply that such a diagnosis will be made easily.

Frequent mental status examinations, at various times throughout the day, may be required to render a diagnosis of delirium. This is generally done using the Mini-Mental State Examination (MMSE). This abbreviated form of mental status examination begins by first assessing the patient's ability to attend. If the patient is inattentive or in a stuporous state, further examination of mental status cannot be done. However, assuming the patient is able to respond to questions asked, the examination can proceed. The Mini-Mental State Exam assesses the areas of orientation, registration, attention and concentration, recall, language, and spatial perception. Another recently evaluated and recommended tool for use in diagnosing delirium is the Delirium Rating Scale-Revised-98. This clinician-rated, 16-item scale allows for the assessment of 13 severity items and three diagnostic items. This test has been reported as more sensitive than the MMSE at detecting delirium.

At times, the untrained observer may mistake psychotic features of delirium for another primary mental illness such as schizophrenia or a manic episode such as that associated with bipolar disorder . However, it should be noted that there are major differences between these diagnoses and delirium. In people who have schizophrenia, their odd behavior, stereotyped motor activity, or abnormal speech persists in the absence of disorientation like that seen with delirium. The schizophrenic appears alert and although his/her delusions and/or hallucinations persist, he/she could be formally tested. In contrast, the delirious patient appears hapless and disoriented, between episodes of lucidity. The delirious patient may not be testable. A manic episode could be misconstrued for agitated delirium, but consistency of elevated mood would contrast sharply to the less consistent mood of the delirious patient. Once again, delirium should always be considered when there is a rapid onset and especially when there is waxing and waning of the ability to attend and the confusion state.

Since delirium can be superimposed into a pre-existing dementia , the most often posed question, when diagnosing delirium, is whether the person might have dementia instead. Both cause disturbances of memory, but a person with dementia does not reflect the disturbance of consciousness depicted by someone with delirium. Expert history taking is a must in differentiating dementia from delirium. Dementia is insidious in nature and thus progresses slowly, while delirium begins with a sudden onset and acute symptoms. A person with dementia can appear clear-headed, but can harbor delusions not elicited during an interview. One does not see the typical fluctuation of consciousness in dementia that manifests itself in delirium. It has been stated that, as a general rule, delirium comes and goes, but dementia comes and stays. Delirium rarely lasts more than a month. Usually, by the end of that period, a patient with dementia has full-blown dementia or has died. As a final caution, the clinician must be prepared to rule out factitious disorder and malingering as possible causes for the delirium.

When a state of delirium is confirmed, the clinician is faced with the task of making the diagnosis in appropriate context to its cause. The delirium may be caused by a general medical condition. In such a case, the clinician must identify the source of the delirium within the diagnosis. For example, if the delirium is caused by liver dysfunction, wherein the liver is unable to clean the system of toxins, thereby allowing them to enter the system and so the brain, the diagnosis would be Delirium Due to Hepatic Encephalopathy. The delirium might also be caused by a substance such as alcohol. To render a diagnosis of Alcohol Intoxication Delirium, the cognitive symptoms should be more exaggerated than those found in intoxication syndrome. The delirium could also be caused by withdrawal from a substance. Continuing the alcohol theme, the diagnosis would be Alcohol Withdrawal Delirium (delirium tremens could be a feature of this diagnosis).

There may be instances in which delirium has multiple causes, such as when a patient has a head trauma and liver failure, or viral encephalitis and alcohol withdrawal. When delirium comes from multiple sources, a diagnosis of delirium precedes each medical condition that contributes. As an example, the multiple causes would be reflected as Delirium Due to Head Trauma and Delirium Due to Hepatic Encephalopathy. Finally, when delirium is the focus of clinical attention, but insufficient evidence exists to identify a specific causal factor, a diagnosis of Delirium Not Otherwise Specified is rendered. An example of this can occur in people who are exposed to sensory deprivation, such as might occur in Intensive Care Units or Cardiac Care Units where the patient is allowed no stimulation save that of the occasional member of the hospital staff.

In summary, delirium develops rapidly, has a fluctuating course involving waxing and waning lucidity, severely affects attention, must receive immediate medical attention, and is reversible in most cases.


Treating delirium means treating the underlying illness that is its basis. This could include correcting any chemical disparities within the body, such as electrolyte imbalances, the treatment of an infection, reduction of a fever, or removal of a medication or toxin. A review of anticholinergic effects of medications administered to the patient should take place. It is suggested that sedatives and hypnotic-type medications not be used; however, despite the fact that they can sometimes contribute to delirium, in cases of agitated delirium, the use of these may be necessary. Medications that are often used to treat agitated delirium include haloperidol , thioridazine and risperidone . These can reduce the psychotic features and curb some of the volatility of the patient, but they are only treating symptoms of the delirium and not the source. Benzodiazepines (medications that slow the central nervous system to relax the patient) can also assist in controlling agitated patients, but since they can contribute to delirium, they should be used in the lowest therapeutic doses possible. The reduction and discontinuance of all psychotropic drugs should be the goal of treatment and occur as soon as possible to permit recovery and viable assessment of the patient.


If a quick diagnosis and treatment of delirium occurs, the condition is frequently reversible. However, if the condition goes unchecked or is treated too late, there is a high incidence of mortality or permanent brain damage associated with it. The underlying illness may respond quickly to a treatment regimen, but improvement in mental functioning may lag behind, especially in the elderly. Moreover, one study disclosed that one group of elderly survivors of delirium, at three years following hospital discharge, had a 33% higher rate of death than other patients. As a final note, delirium is a medical emergency, requiring prompt attention to avoid the potential for permanent brain damage or even death.



American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th edition, text revised. Washington, DC: American Psychiatric Association, 2000.

Kaplan, Harold and Benjamin Sadock. Synopsis of Psychiatry. 8th edition. New York: Lippincott, Williams and Wilkins, 1997.

The Merck Manual. 17th edition. Whitehouse Station, N.J.: Merck Research Laboratories, 1999.


Chan, Daniel. "Delirium: Making the diagnosis, improving the prognosis." Geriatrics 54 (1999): 28-42.

Curyto, Kim J., Jerry Johnson, Thomas TenHave, Jana Mossey, Kathryn Knott, and Ira R. Katz. "Survival of Hospitalized Elderly Patients With Delirium: A Prospective Study." American Journal of Geriatric Psychiatry 9 (2001): 141-147.

Katz, Ira R., Kim J. Curyto, Thomas TenHave, Jana Mossey, Laura Sands, and Michael Kallan. "Validating the Diagnosis of Delirium and Evaluating its Association With Deterioration Over a One-Year Period." American Journal of Geriatric Psychiatry 9 (2001): 148-159.

Trzepacz, Paula T. "The Delirium Rating Scale: Its Use in Consultation-Liaison Research." Psychosomatics 40 (1999): 193-204.

Trzepacz, Paula T., Dinesh Mittal, Rafael Torres, Kim Kanary, John Norton, and Nita Jimerson. "Validation of The Delirium Rating Scale-Revised-98: Comparison with the delirium rating scale and the cognitive test for delirium." Journal of Neuropsychiatry and Clinical Neuroscience 13 (2001): 229-242.

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Jack H. Booth, Psy.D.

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User Contributions:

Diana Hill
My mother was diagnosed with delirum. She is 81 years old. She's had recent surgery (in Sept 2010) and went downhill after that. She had another surgery for bleeding 2 days after surgery for heart valve replacement. At times she is out of her mind then it quits and she is totally lucid for a while. UTI was the reason for 2 times but when that was cleared up, the only infection she had was 4 teeth that needed to be pulled and she had been on an antibiotic. My question is 1) Could infected teeth cause a horrific episode even though taking antibiotics? In the space of two months (she is in a nursing home now) she had the flu, then UTI, then the Hives which sent her to the hospital, then the infected teeth. 1 week after the teeth were removed, she was totally lucid. She is pressing hard to leave the nursing home and wants to go home but she will be alone. Do these episodes come and go?
maggie fisher
Hello there wonder if you can help,my mother has been talking about my dad as though he is still around the house he has been dead for over twenty years,also the dogs we lost many years ago.The way she talks you would think they were are all alive. She is nearly 84 and was very active until about 1 year ago. She has heart problems and blackouts. It is so sad to see her like this what causes this and is there treatments for this.
Lesley Mallia
My mother in Law had a hip operation around 6th January and has been diagnosed with Delirium, after operation she was disorientated and unable to sleep at night just wanted to leave hospital now some 6 weeks later she is still in hospital, tried to take her to the canteen for change of scenary and she became confused and we had to return to her room. The staff say she is very disruptive everynight and disturbs whole ward will not stay in bed, even tried getting in someone else's bed. When we visit she is able to recognise us but just rambles is coherant but very confused and jumps from one subject to another,, tries to disrobe all the time, complains about her knee hurting and always rolling trousers up. Yet if you ask her to speak her native tongue Maltese she does it with ease, can count in several languages. Obviously it is very distressing, what stage do you think she is at, will she recover, will she be able to come home, what do you think the prognosis and will she survive or will she have heart attack? what is the normal length of time as i read after 1 month theres no return and its classed as servere. Lots of question I know , please can you help as very concerned.
Mrs Sandra Twells
My mum has developed delirium following surgery after a nasty fall she is as I text Sat in a hospital chair as she is refusing medication,food and fluids by the time7.30am comes on the 3/2/18 she will have been there for 24hrs she has had no sleep and is severely sleep deprived she was to be discharged today but due to adverse weather conditions unfortunately no ambulance and has become really upset and this is the outcome what can I do I feel we will lose our mum as her symptoms are not being treated please advise asap

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