Delirium or acute confusional state is a common and severe neuropsychiatric syndrome with core features of acute onset and fluctuating course, attentional deficits and generalized severe disorganization of behavior. It typically involves other cognitive deficits, changes in arousal (hyperactive, hypoactive, or mixed), perceptual deficits, altered sleep-wake cycle, and psychotic features such as hallucinations and delusions. It is often caused by a disease process outside the brain, such as infection (urinary tract infection
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...

, pneumonia) or drug effects, particularly anticholinergic
An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....

s or other CNS depressants (benzodiazepines and opioids). Although hallucinations and delusions are sometimes present, these are not required for the diagnosis, and the symptoms of delirium are clinically distinct from those induced by psychosis
Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...

 or hallucinogens (with the exception of deliriant
The deliriants are a special class of acetylcholine-inhibitor hallucinogen. The term was introduced by David F. Duncan and Robert S...


Delirium itself is not a disease, but rather a clinical syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...

 (a set of symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

s), which result from an underlying disease or new problem with mentation. Like its components (inability to focus attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....

, mental confusion
Mental confusion
Confusion of a pathological degree usually refers to loss of orientation sometimes accompanied by disordered consciousness and often memory Confusion (from Latin confusĭo, -ōnis, noun of action from confundere "to pour together", also "to confuse") of a pathological degree usually refers to loss...

 and various impairments in awareness and temporal and spatial orientation), delirium is simply the common symptomatic manifestation of early brain or mental dysfunction (for any reason). Without careful assessment, delirium can easily be confused with a number of psychiatric disorders because many of the signs and symptoms are conditions present in dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

, depression
Mood disorder
Mood disorder is the term designating a group of diagnoses in the Diagnostic and Statistical Manual of Mental Disorders classification system where a disturbance in the person's mood is hypothesized to be the main underlying feature...

, and psychosis
Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...


Treatment of delirium requires treatment of the underlying causes. In some cases, temporary or palliative or symptomatic treatments are used to comfort patients or to allow better patient management (for example, a patient who, without understanding, is trying to pull out a ventilation tube that is required for survival). Delirium is probably the single most common acute disorder affecting adults in general hospitals. It affects 10-20% of all hospitalized adults, and 30-40% of elderly hospitalized patients and up to 80% of ICU
Intensive Care Unit
thumb|220px|ICU roomAn intensive-care unit , critical-care unit , intensive-therapy unit/intensive-treatment unit is a specialized department in a hospital that provides intensive-care medicine...



In common usage, delirium is often used to refer to drowsiness, disorientation, and hallucination. In broader medical terminology
Medical terminology
Medical terminology is a vocabulary for accurately describing the human body and associated components, conditions, processes and process in a science-based manner. Some examples are: R.I.C.E., trapezius, and latissimus dorsi. It is to be used in the medical and nursing fields...

, however, a number of other symptoms, including a sudden inability to focus attention, and even (occasionally) sleeplessness and severe agitation and irritability, also define "delirium," and hallucination, drowsiness, and disorientation are not required.

There are several medical definitions of delirium (including those in the DSM-IV
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

 and ICD-10
The International Statistical Classification of Diseases and Related Health Problems is a medical classification that provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or disease...

). However, all include some core features.

The core features are:
  • Disturbance of consciousness (that is, reduced clarity of awareness of the environment, with reduced ability to focus, sustain, or shift attention)
  • Change in cognition (e.g., problem-solving impairment or memory impairment) or a perceptual disturbance
  • Onset of hours to days, and tendency to fluctuate.
  • Behaviour may be either overactive or underactive. Sleep is often disturbed.
  • Thinking is slow and muddled but the content is often complex.

Common features also tend to include:
  • Intrusive abnormalities of awareness and affect
    Affect (psychology)
    Affect refers to the experience of feeling or emotion. Affect is a key part of the process of an organism's interaction with stimuli. The word also refers sometimes to affect display, which is "a facial, vocal, or gestural behavior that serves as an indicator of affect" .The affective domain...

    , such as hallucination
    A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...

    s or inappropriate emotional states.

Signs and symptoms

Since delirium may occur in very many grades of severity, all symptoms may occur with varying degrees of intensity. A mild disability to focus attention may result in only a disability in solving the most complex problems. As an extreme example, a mathematician with the flu may be unable to perform creative work, but otherwise may have no difficulty with basic activities of daily living. However, as delirium becomes more severe, it disrupts other mental functions, and may be so severe that it borders on unconsciousness or a vegetative state. In the latter state, a person may be awake and immediately aware and responsive to many stimuli, and capable of coordinated movements, but unable to perform any meaningful mental processing task at all.

Delirium may be of a hyperactive variety manifested by 'positive' symptoms of agitation or combativeness, or it may be of a hypoactive variety (often referred to as 'quiet' delirium) manifested by 'negative' symptoms such as inability to converse or focus attention or follow commands. While the common non-medical view of a delirious patient is one who is hallucinating, most people who are medically delirious do not have either hallucinations or delusions. Delirium is commonly associated with a disturbance of consciousness (e.g., reduced clarity of awareness of the environment). The change in cognition (memory deficit, disorientation, language disturbance) or the development of a perceptual disturbance, must be one that is not better accounted for by a pre-existing, established, or evolving dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

. Usually the rapidly fluctuating time course of delirium is used to help in the latter distinction.


The delirium-sufferer loses the capacity for clear and coherent thought. This may be apparent in disorganised or incoherent speech, the inability to concentrate (focus attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....

), or in a lack of any goal-directed thinking. These limitations in thought may also be manifested as purposeless behavior, such as rummaging or punding, or as a difficulty completing a single purpose-oriented task - to the extent that a delirious individual may engage in a string of incomplete and unrelated activities.

Disorientation (another symptom of confusion, and usually a more severe one) describes the loss of awareness of the surroundings, environment and context in which the person exists. It may also appear with delirium, but it is not required, as noted. Disorientation may occur in time (not knowing what time of day, day of week, month, season or year it is), place (not knowing where one is) or person (not knowing who one is).

Cognitive function may be impaired enough to make medical criteria for delirium, even if orientation is preserved. Thus, a patient who is fully aware of where they are and who they are, but cannot think because they cannot concentrate, may be medically delirious. The state of delirium most familiar to the average person is that which occurs from extremes in pain, lack of sleep, or emotional shock.

Because most high level mental skills are required for problem solving
Problem solving
Problem solving is a mental process and is part of the larger problem process that includes problem finding and problem shaping. Consideredthe most complex of all intellectual functions, problem solving has been defined as higher-order cognitive process that requires the modulation and control of...

, including ability to focus attention, this ability also suffers in delirium. However, this is a secondary phenomenon, since problem-solving involves many sub-skills and basic mental abilities, any of which may be impaired in a delirious patient.

Memory formation

Impairments to cognition may include temporary reduction in the ability to form short-term or long-term memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

. Difficult short-term memory tasks like ability to repeat a phone number may be continuously disrupted during a delirium, but easier short-term memory tasks like repeating single words, or remembering simple questions long enough to give an answer, may not be impaired. Reduction in formation of new long-term memory (which by definition survive withdrawal of attention), is common in delirium, because initial formation of (new) long-term memories generally requires an even higher degree of attention, than do short-term memory tasks. Since older memories are retained without need of concentration, previously formed long-term memories (i.e., those formed before the period of delirium) are usually preserved in all but the most severe cases of delirium (and when destroyed, are destroyed by the underlying brain pathology, not the delirious state per se).

Awareness and affect

A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...

s (perceived sensory experience with the lack of an external source) or distortions of reality may occur in delirium, but they are not essential for the diagnosis. Commonly these are visual distortions, and can take the form of masses of small crawling creatures (particularly common in delirium tremens
Delirium tremens
Delirium tremens is an acute episode of delirium that is usually caused by withdrawal from alcohol, first described in 1813...

, caused by severe alcohol withdrawal) or distortions in size or intensity of the surrounding environment.

Strange belief
Belief is the psychological state in which an individual holds a proposition or premise to be true.-Belief, knowledge and epistemology:The terms belief and knowledge are used differently in philosophy....

s may also be held during a delirious state, but these are not considered fixed delusion
A delusion is a false belief held with absolute conviction despite superior evidence. Unlike hallucinations, delusions are always pathological...

s in the clinical sense as they are considered too short-lived (i.e., they are temporary delusions - such as thinking that a nurse is a person from his/her past trying to cause injury). Interestingly, in some cases sufferers may be left with false or delusional memories after delirium, basing their memories on the confused thinking or sensory distortion which occurred during the episode of delirium. Other instances would be inability to distinguish reality from dreams.

Abnormalities of affect which may attend the state of delirium may include many distortions to perceived or communicated emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

al states. Emotional states may also fluctuate, so that a delirious person may rapidly change between, for example, terror, sadness and jocularity.


The duration of delirium is typically affected by the underlying cause. If caused by a fever, the delirious state often subsides as the severity of the fever subsides. However, it has long been suspected that in some cases delirium persists for months and that it may even be associated with permanent decrements in cognitive function. Barrough said in 1583 that if delirium resolves, it may be followed by a "loss of memory and reasoning power." Recent studies bear this out, with cognitively normal patients who suffer an episode of delirium carrying an increased risk of dementia in the years that follow. In many such cases, however, delirium undoubtedly does not have a causal nature, but merely functions as a temporary unmasking with stress, of a previously unsuspected (but well-compensated) state of minimal brain dysfunction (early dementia).


Delirium is a very general and nonspecific symptom of organ dysfunction, where the organ in question is the brain. Delirium may be caused by physical illness, which can be mild, or any process which interferes with the normal metabolism or function of the brain. For example, electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....

, fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

, pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

, poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

s (including toxic drug
Approved drug
In the United States, the FDA approves drugs. Before a drug can be prescribed, it must undergo an extensive FDA approval process. This process involves first testing the drug on animals or in medical labs. If found to be safe by the FDA and approved for the next phase of study, the drug is then...

 reactions), brain injury, hypoxia, anoxia, surgery, traumatic shock, lack of food or water or sleep, and even withdrawal symptoms of certain drug and alcohol
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...

 dependent states, are all known to cause delirium. In addition, there is an interaction between acute and chronic symptoms of brain dysfunction; delirious states are more easily produced in people already suffering with underlying chronic brain dysfunction.

Critical illness

The most common behavioral manifestation of acute brain dysfunction is delirium, which occurs in up to 60% to 80% of mechanically ventilated medical and surgical ICU patients and 50% to 70% of non-ventilated medical ICU patients. During the ICU stay, acute delirium is associated with complications of mechanical ventilation including nosocomial pneumonia, self-extubation, and reintubation. ICU delirium predicts a 3- to 11-fold increased risk of death at 6 months even after controlling for relevant covariates such as severity of illness. Of late, delirium has been recognized by some as a sixth vital sign, and it is recommended that delirium assessment be a part of routine ICU management. The elderly may be at particular risk for this spectrum of delirium and dementia. A firm understanding of the pathophysiologic mechanisms of delirium remains elusive despite improved diagnosis and potential treatments.

Substance withdrawal

Drug withdrawal is a common cause of delirium. The most notable are alcohol withdrawal and benzodiazepine withdrawal but other drug withdrawals both from licit and illicit drugs can sometimes cause delirium.

Gross structural brain disorders

  • Head trauma (i.e., concussion, traumatic bleeding, penetrating injury, etc.)
  • Gross structural damage from brain disease (stroke, spontaneous bleeding, tumor, etc.)

Neurological disorders

  • Various neurological disorders
  • Lack of sleep
    Sleep deprivation
    Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the...


  • Hypoxia
    Hypoxia (medical)
    Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

  • Hypoglycemia
    Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

  • Electrolyte
    In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

     imbalance (dehydration, water intoxication)


  • Medication
    A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

    s including psychotropic medications, opiates and benzodiazepines.


  • Intoxication various drugs
    Destroy Rebuild Until God Shows are an American post-hardcore band formed in 2010. They released their debut self-titled album on February 22, 2011.- Formation :...

    , alcohol
    Alcoholic beverage
    An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...

    , anesthetics
  • Sudden withdrawal of chronic drug use in a person with certain types of drug addiction (e.g. alcohol, see delirium tremens
    Delirium tremens
    Delirium tremens is an acute episode of delirium that is usually caused by withdrawal from alcohol, first described in 1813...

    , and many other sedating drugs)
  • Poisons (including carbon monoxide
    Carbon monoxide
    Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

     and metabolic blockade)

Mental illness

Some mental illnesses, such as mania, or some types of acute psychosis, may cause a rapidly fluctuating impairment of cognitive function and ability to focus. However, they are not technically causes of delirium, since any fluctuating cognitive symptoms that occur as a result of these mental disorders are considered by definition to be due to the mental disorder itself, and to be a part of it. Thus, physical disorders can be said to produce delirium as a mental side-effect or symptom, although primary mental disorders which produce the symptom cannot be put into this category once identified. However, such symptoms may be impossible to distinguish clinically from delirium resulting from physical disorders, if a diagnosis of an underlying mental disorder has yet to be made.


Differential points from other processes and syndromes that cause cognitive dysfunction:
  • Delirium may be distinguished from psychosis
    Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...

    , in which consciousness and cognition may not be impaired (however, there may be overlap, as some acute psychosis, especially with mania, is capable of producing delirium-like states).
  • Delirium is distinguished from dementia
    Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

     (chronic organic brain syndrome) which describes an "acquired" (non-congenital) and usually irreversible cognitive and psychosocial decline in function. Dementia usually results from an identifiable degenerative brain disease (for example Alzheimer disease or Huntington's disease
    Huntington's disease
    Huntington's disease, chorea, or disorder , is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and dementia. It typically becomes noticeable in middle age. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea...

    ). Dementia is usually not associated with a change in level of consciousness, and a diagnosis of dementia requires a chronic impairment.
  • Delirium is distinguished from depression
    Clinical depression
    Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

  • Delirium is distinguished by time-course from the confusion and lack of attention which result from long term learning disorders and varieties of congenital brain dysfunction. Delirium has also been referred to as 'acute confusional state' or 'acute brain syndrome'. The key word in both of these descriptions is "acute" (meaning: of recent onset), since delirium may share many of the clinical (i.e., symptomatic) features of dementia, developmental disability
    Developmental disability
    Developmental disability is a term used in the United States and Canada to describe lifelong disabilities attributable to mental or physical impairments, manifested prior to age 18. It is not synonymous with "developmental delay" which is often a consequence of a temporary illness or trauma during...

    , or attention-deficit hyperactivity disorder
    Attention-deficit hyperactivity disorder
    Attention deficit hyperactivity disorder is a developmental disorder. It is primarily characterized by "the co-existence of attentional problems and hyperactivity, with each behavior occurring infrequently alone" and symptoms starting before seven years of age.ADHD is the most commonly studied and...

    , with the important exception of symptom duration.
  • Delirium is not the same as confusion, although the two syndromes may overlap and be present at the same time. However, a confused patient may not be delirious (an example would be a stable, demented person who is disoriented to time and place), and a delirious person may not be confused (for example, a person in severe pain may not be able to focus attention because of the pain, and thus by definition delirious, but may be completely oriented and not at all confused).

It is a corollary of the above differential criteria that a diagnosis of delirium cannot be made without a previous assessment, or knowledge, of the affected person's baseline level of cognitive function. In other words, a mentally disabled or demented person who is operating at their own baseline level of mental ability might appear to be delirious without a baseline functional status against which to compare.

Several valid and reliable rating scales now exist which can be used to accurately diagnose delirium by trained individuals.


Episodes of delirium can be prevented by identifying hospitalized people at risk of the condition: those over 65, those with a known cognitive impairment, those with hip fracture
Hip fracture
A hip fracture is a femoral fracture that occurs in the proximal end of the femur , near the hip.The term "hip fracture" is commonly used to refer to four different fracture patterns and is often due to osteoporosis; in the vast majority of cases, a hip fracture is a fragility fracture due to a...

, those with severe illness. Close observation for the early signs is recommended in those people. Systematically addressing the common contributing factors (such as constipation, dehydration and polypharmacy), as well as providing adequate lighting, signage and ways to tell the time, may prevent delirium.

It is thought that 30–40% of all cases of delirium could be prevented, and that high rates of delirium reflect negatively on the quality of care.


Treatment of delirium involves two main strategies. First, treatment of the underlying presumed acute cause or causes. Second, optimising conditions for the brain. This involves ensuring that the patient with delirium has adequate oxygenation, hydration, nutrition, and normal levels of metabolites, that drug effects are minimised, constipation treated, pain treated, and so on. Detection and management of mental stress is also very important. Thus, the traditional concept that the treatment of delirium is 'treat the cause' is not adequate; patients with delirium actually require a highly detailed and expert analysis of all the factors which might be disrupting brain function.

Non-pharmacological treatments are the first measure in delirium, unless there is severe agitation that places the person at risk of harming oneself or others. Avoiding unnecessary movement, involving family members, having recognizable faces at the bedside, having means of orientation available (such as a clock and a calendar) may be sufficient in stabilizing the situation. If this is insufficient, verbal and non-verbal de-escalation techniques may be required to offer reassurances and calm the person experiencing delirium. Only if this fails, or if de-escalation techniques are inappropriate, is pharmacological treatment indicated.

The pharmacological treatment for delirium depends on its cause. Antipsychotics, particularly haloperidol
Haloperidol is a typical antipsychotic. It is in the butyrophenone class of antipsychotic medications and has pharmacological effects similar to the phenothiazines....

, are the most commonly used drugs for delirium and the most studied. Evidence is weaker for the atypical antipsychotic
Atypical antipsychotic
The atypical antipsychotics are a group of antipsychotic tranquilizing drugs used to treat psychiatric conditions. Some atypical antipsychotics are FDA approved for use in the treatment of schizophrenia...

s, such as risperidone
Risperidone is a second generation or atypical antipsychotic, sold under the trade name . It is used to treat schizophrenia , schizoaffective disorder, the mixed and manic states associated with bipolar disorder, and irritability in people with autism...

, olanzapine
Olanzapine is an atypical antipsychotic, approved by the FDA for the treatment of schizophrenia and bipolar disorder...

 and quetiapine
Quetiapine , is an atypical antipsychotic approved for the treatment of schizophrenia, and bipolar disorder....

. British professional guidelines by the National Institute for Health and Clinical Excellence
National Institute for Health and Clinical Excellence
The National Institute for Health and Clinical Excellence is a special health authority of the English National Health Service , serving both English NHS and the Welsh NHS...

 advise haloperidol or olanzapine
Olanzapine is an atypical antipsychotic, approved by the FDA for the treatment of schizophrenia and bipolar disorder...


Benzodiazepines themselves can cause delirium or worsen it, and lack a reliable evidence base. However, if delirium is due to alcohol withdrawal or benzodiazepine withdrawal or if antipsychotics are contraindicated (e.g. in Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

 or neuroleptic malignant syndrome
Neuroleptic malignant syndrome
Neuroleptic malignant syndrome is a life- threatening neurological disorder most often caused by an adverse reaction to neuroleptic or antipsychotic drugs...

), then benzodiazepines are recommended. Similarly, people with dementia with Lewy bodies
Dementia with Lewy bodies
Dementia with Lewy bodies , also known under a variety of other names including Lewy body dementia, diffuse Lewy body disease, cortical Lewy body disease, and senile dementia of Lewy type, is a type of dementia closely allied to both Alzheimers and Parkinson's Diseases...

 may have significant side-effects to antipsychotics, and should either be treated with a small dose or not at all.

The antidepressant trazodone
Trazodone is an antidepressant of the serotonin antagonist and reuptake inhibitor class. It is a phenylpiperazine compound...

 is occasionally used in the treatment of delirium, but it carries a risk of oversedation, and its use has not been well studied.


The highest prevalence of delirium (often 50% to 75% of patients) is generally seen in critically ill patients in the intensive care unit or ICU (which used to be referred to by the misnomers "ICU psychosis" or "ICU syndrome", terms largely abandoned for the more widely accepted and scientifically supported term delirium). Since the advent of validated and easy to implement delirium instruments for ICU patients such as the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Delirium Screening Checkllist (IC-DSC). Of the hundreds of thousands of ICU patients develop delirium in ICUs every year, it has been recognized that most of them being of the hypoactive variety that is easily missed and invisible to the managing teams unless actively monitored using such instruments. The causes of delirium in such patients depend on the underlying illnesses, new problems like sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

 and low oxygen levels, and the sedative and pain medicines that are nearly universally given to all ICU patients. Outside the ICU, on hospital wards and in nursing homes, the problem of delirium is also a very important medical problem, especially for older patients. The most recent area of the hospital in which delirium is just beginning to be monitored routinely in many centers is the Emergency Department.

A systematic review of delirium in general medical inpatients showed that estimates of delirium prevalence on admission ranged from 10 to 31%.

Society and culture

Delirium is one of the oldest forms of mental disorder known in medical history.

Sims (1995, p. 31) points out a "superb detailed and lengthy description" of delirium in The Stroller's Tale from Charles Dickens
Charles Dickens
Charles John Huffam Dickens was an English novelist, generally considered the greatest of the Victorian period. Dickens enjoyed a wider popularity and fame than had any previous author during his lifetime, and he remains popular, having been responsible for some of English literature's most iconic...

' The Pickwick Papers
The Pickwick Papers
The Posthumous Papers of the Pickwick Club is the first novel by Charles Dickens. After the publication, the widow of the illustrator Robert Seymour claimed that the idea for the novel was originally her husband's; however, in his preface to the 1867 edition, Dickens strenuously denied any...

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