Delirium is a mental state in which you are confused, disoriented, and not able to think or remember clearly. It usually starts suddenly. It is often temporary and treatable.

There are three types of delirium:

• Hypoactive, when you are not active and seem sleepy, tired, or depressed
• Hyperactive, when you are restless or agitated
• Mixed, when you change back and forth between being hypoactive and hyperactive

There are many different problems that can cause delirium. Some of the more common causes include:

• Advanced cancer.
• Alcohol or drugs, either from intoxication or withdrawal. This includes a serious type of alcohol withdrawal syndrome called delirium tremens. It usually happens to people who stop drinking after years of alcohol use disorder (AUD).
• Dehydration and electrolyte imbalances.
• Dementia.
• Hospitalization, especially in intensive care.
• Infections, such as urinary tract infections, pneumonia, and the flu.
• Medicines. This could be a side effect of a medicine, such as sedatives or opioids. Or it could be from withdrawal after stopping a medicine.
• Metabolic disorders.
• Organ failure, such as kidney or liver failure.
• Poisoning.
• Serious illnesses.
• Severe pain.
• Sleep deprivation.
• Surgeries, including reactions to anesthesia.

Certain factors put you at risk for delirium, including:

• Being in a hospital or nursing home
• Having dementia
• Having a serious illness or more than one illness
• Having an infection
• Older age
• Having surgery
• Taking medicines that affect the mind or behavior
• Taking high doses of pain medicines, such as opioids

The symptoms of delirium usually start suddenly, over a few hours or a few days. They often come and go. The most common symptoms include:

• Changes in alertness (usually more alert in the morning, less at night)
• Changing levels of consciousness
• Confusion
• Disorganized thinking, talking in a way that doesn't make sense
• Disrupted sleep patterns, sleepiness
• Emotional changes: anger, agitation, depression, irritability, overexcitement
• Hallucinations and delusions
• Memory problems, especially with short-term memory
• Trouble concentrating

Your health care provider may use many tools to make a diagnosis:

• A medical history, which includes asking about your symptoms
• Physical and neurological exams
• Mental status testing, which checks for problems with your thinking and alertness
• Lab and diagnostic imaging tests

Delirium and dementia have similar symptoms, so it can be hard to tell them apart. You can also have both at the same time. The differences between them are that:

• Delirium starts suddenly and can cause hallucinations. It is mainly a problem with attention and staying alert. The symptoms may get better or worse and can last for hours or weeks.
• Dementia develops slowly and does not cause hallucinations. It usually starts with memory loss. The symptoms don't change often, like they can with delirium. Dementia almost never gets better.

Treatment of delirium focuses on the causes and symptoms of delirium. The first step is to identify the cause. Often, treating the cause will lead to a full recovery. The recovery may take some time - weeks or sometimes even months. In the meantime, there may be treatments to manage the symptoms, such as:

• Controlling the environment, which includes making sure that the room is quiet and well-lit, having clocks or calendars in view, and having family members around
• Medicines, including those that control aggression or agitation and pain relievers if there is pain
• If needed, making sure that the person has a hearing aid, glasses, or other devices for communication

Treating the conditions that can cause delirium may reduce the risk of getting it. Hospitals can help lower the risk of delirium by avoiding sedatives and making sure that hospital rooms are kept quiet, calm, and well-lit. It can also help to have family members around and to have the same staff members treat the person each day (if possible).