Delirium happens when a person has sudden confusion or a sudden change in mental status. The person may have trouble paying attention or thinking clearly. They may act disoriented or distracted.

Delirium is more severe than having a “senior moment” — the minor problems people have with memory and understanding as they get older. It requires treatment and often hospitalization.

Delirium and dementia

Dementia and delirium may be particularly difficult to distinguish, and a person may have both. In fact, delirium frequently occurs in people with dementia. But having episodes of delirium does not always mean a person has dementia. So a dementia assessment should not be done during a delirium episode because the results could be misleading.

Dementia is the progressive decline of memory and other thinking skills due to the gradual dysfunction and loss of brain cells. The most common cause of dementia is Alzheimer's disease.

Some differences between the symptoms of delirium and dementia include:

·       Onset. The onset of delirium occurs within a short time, while dementia usually begins with relatively minor symptoms that gradually worsen over time.

·       Attention. The ability to stay focused or maintain attention is significantly impaired with delirium. A person in the early stages of dementia remains generally alert.

·       Fluctuation. The appearance of delirium symptoms can fluctuate significantly and frequently throughout the day. While people with dementia have better and worse times of day, their memory and thinking skills stay at a fairly constant level during the course of a day.

Types of delirium

Delirium is categorized by its cause, severity, and characteristics:

Symptoms of hyperactive delirium include:

·       Acting disoriented.

·       Anxiety.

·       Hallucinations.

·       Rambling.

·       Rapid changes in emotion.

·       Restlessness.

·       Trouble concentrating.

Symptoms of hypoactive delirium include:

·       Apathy.

·       Decreased responsiveness.

·       Flat affect.

·       Laziness.

·       Withdrawal.


Some people have a combination of both hyperactive and hypoactive delirium (called mixed delirium), alternating between the two states.


Signs and symptoms of delirium usually begin over a few hours or a few days. They often fluctuate throughout the day, and there may be periods of no symptoms. Symptoms tend to be worse during the night when it's dark and things look less familiar. Primary signs and symptoms include those below.

Reduced awareness of the environment

This may result in:

·       An inability to stay focused on a topic or to switch topics

·       Getting stuck on an idea rather than responding to questions or conversation

·       Being easily distracted by unimportant things

·       Being withdrawn, with little or no activity or little response to the environment

Poor thinking skills (cognitive impairment)

This may appear as:

·       Poor memory, particularly of recent events

·       Disorientation — for example, not knowing where you are or who you are

·       Difficulty speaking or recalling words

·       Rambling or nonsense speech

·       Trouble understanding speech

·       Difficulty reading or writing

Behavior changes

These may include:

·       Seeing things that don't exist (hallucinations)

·       Restlessness, agitation or combative behavior

·       Calling out, moaning or making other sounds

·       Being quiet and withdrawn — especially in older adults

·       Slowed movement or lethargy

·       Disturbed sleep habits

·       Reversal of night-day sleep-wake cycle

Emotional disturbances

These may appear as:

·       Anxiety, fear or paranoia

·       Depression

·       Irritability or anger

·       A sense of feeling elated (euphoria)

·       Apathy

·       Rapid and unpredictable mood shifts

·       Personality changes


Medical professionals do not know the exact cause of delirium. However, inflammation of the brain, imbalances in neurotransmitters, and chronic stress may all play a role in the onset of symptoms.

Causes of delirium can include: