Acute confusional state, more commonly known as delirium, is a state of impaired consciousness, cognitive functioning, and perception. The condition's "acute" designation means it can appear within hours or days, and it can be resolved in hours, days, weeks, or months, depending on the cause and severity of the impairment. Although it is not permanent, delirium does require medical attention, and it may be life-threatening if the person experiencing the acute confusional state is left alone.


The symptoms of delirium are broken down into four categories.

  • Category one: reduced awareness of the environment, such as an inability to keep up with a conversation, being easily distracted or lacking the ability to focus on things, withdrawal from the environment, and a lack of response to things going on in the environment.
  • Category two: thinking skills like poor memory, disorientation, rambling or nonsense speech, difficulty recalling words or speaking, trouble understanding speech, and difficulty reading or writing.
  • Category three: behavioral changes, including hallucinations, disturbance or reversal of sleep patterns, lethargy, restless, agitated, or combative behavior, and moaning, calling out, or making other unusual noises.
  • Category four: Emotional disturbances like personality changes, unpredictable mood changes, sudden paranoia, anxiety, fear, irritability, or depression.

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Research identifies three types of delirium.

  • Hyperactive delirium is the most easily recognized and includes restless movements like pacing, agitation, rapid mood changes, and a refusal to cooperate with caregivers. Hallucinations may also develop.
  • Hypoactive delirium is characterized by lack of motor activity, general sluggishness, abnormal drowsiness, and dazed appearance.
  • Mixed delirium includes symptoms from both types, and the person may switch back and forth.

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To diagnose an acute confusional state or delirium, a doctor will perform a psychological evaluation to rule out mental health conditions. A physical and neurological exam can help the physician check for injuries. Urine and blood tests can determine the levels of medications or alcohol in the person's system.

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Many underlying issues can trigger an episode of delirium. Often, the state develops due to a chronic illness combined with a high fever, infection, dehydration, sleep deprivation, changes in metabolic balance such as a sodium imbalance, certain medications including allergy and pain medications, surgery, head injury, and substance abuse or withdrawal.

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Risk Factors

Research suggests certain risk factors can increase the chance of experiencing an acute confusional state. Old age, stroke, and a previous delirium episode make it more likely an individual will experience the condition. Dehydration and visual or hearing impairments are also risk factors for experiencing an acute confusional state.

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Delirium vs. Dementia

Although they have similar symptoms, delirium and dementia are different condition. Dementia is a degenerative condition that worsens slowly over time. Though delirium can be a symptom of dementia, it is distinguished by the sudden onset of symptoms as well as the fluctuating, reversible nature of the impairment. Research also shows that an acute confusional state may worsen at night, unlike dementia.

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Delirium vs. Dissociative Fugue

Delirium and dissociative fugue seem similar because of their sudden onset, memory loss, and the chance they will spontaneously resolve, but these two conditions are very different. A dissociative fugue state, a type of amnesia, differs from an acute confusional state because the former is always caused by extreme stress or a psychologically traumatic event, after which a person will forget only their biographical information. A person in dissociative fugue will flee. A delirium episode does not involve forgetting all autobiographical information or fleeing the scene of the traumatizing trigger.

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People in a state of delirium may experience some complications as a result of their condition. They won't remember if they ate, drank, or took vital medications. The disturbances to the person's sleep schedule may mean they now need around-the-clock care, which can be expensive. They may also have a harder time recovering from surgery. Disorientation may present life-threatening problems if they go out unattended.

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The only treatment for an acute confusional state is to address the underlying conditions, though even this will not immediately cure the delirium unless it is caused by a substance, high fever, or dehydration. As such, the person still needs care until the delirium subsides. They may require hospitalization.

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Research indicates that certain strategies may prevent or reduce the severity of delirium episodes. Good sleep habits, staying up-to-date on medical issues, and maintaining a calm, familiar environment to help the person stay well-oriented can help reduce the frequency and severity of the episodes.

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