Delirium is a sudden change in a person's mental state that varies over short periods of time. It can cause a person to have a hard time paying attention or have a conversation. Their thinking and speech may not make sense and be random. A person's mental state may change from being restless and alert to slow and sleepy. At times, the person can be confused, argue, and see or hear things that you don't.

Delirium is a medical emergency. If it's not diagnosed and treated, it can lead to lasting problems or death.

Delirium most often affects older adults. People are also at greater risk if they have existing brain problems, such as a past stroke. Delirium can happen when a person is in an unfamiliar place, such as a hospital. It's common after surgery or during a serious illness. Drug use or withdrawal from drug or alcohol use can cause it. Some medicines can cause it. And toxins and infections can cause it. A disease that affects the kidneys or liver can cause toxins to build up in the body. This can cause delirium. Not enough oxygen due to lung disease can cause it.

In most cases, something triggers the delirium. Often, it may be the first sign that a person has dementia. But dementia is a different condition. It's permanent and usually gets worse over months or years.

Delirium can be upsetting for family and friends to see. But steps can be taken to help manage it. These can help ensure your loved one's safety and comfort.

The signs of delirium can come and go over hours or days. A person may:

• Seem sleepy and quiet
• Be confused*
• Have trouble paying attention and focusing*
• Not know where they are*
• See or hear things that others can't see or hear (hallucinations)
• Believe things that aren't known to be true (delusions)
• Think that people want to harm the person (paranoia)
• Have trouble remembering things that just happened*
• Change the subject too often while talking
• Talk about things that may not make sense*
• Seem restless and alert
• Become violent*
• Have less interest in eating*
• Seem to be depressed and not interested in doing things*
• Have quick emotional changes, such as anxiety or sadness, or strong moods of joy and excitement (euphoria)
• Be unsteady while walking*
• Have twitching or stiff movement in the arms, legs, or neck*

*These symptoms can happen with dementia and also with other health problems. Talk with a doctor if a person has these.

Delirium is a medical emergency. If you think a person has delirium, get medical help right away. If the person is at home, call 911. If they're in the hospital, tell a doctor right away.