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What is a hallucination?
A hallucination is a false perception of objects or events involving your senses: sight, sound, smell, touch and taste. Hallucinations seem real, but they’re not. Chemical reactions and/or abnormalities in your brain cause hallucinations.
Hallucinations are typically a symptom of a psychosis-related disorder, particularly schizophrenia, but they can also result from substance use, neurological conditions and some temporary situations.
A person may experience a hallucination with or without the insight that what they’re experiencing isn’t real. When a person thinks their hallucination is real, it’s considered a psychotic symptom.
What are the types of hallucinations?
There are several different types of hallucinations, including:
- Auditory (sound) hallucinations: These are the most common type of hallucinations. They involve hearing sounds that aren’t real, like music, footsteps or doors banging. Some people hear voices when no one has spoken. The voices may be positive, negative or neutral. They may command you to do something that may cause harm to yourself or others.
- Visual (sight) hallucinations: These hallucinations involve seeing things that aren’t real, like objects, shapes, people, animals or lights.
- Tactile (touch) hallucinations: These hallucinations cause you to feel touch on your body or movement in your body that’s not real. They may involve feeling like bugs are crawling on your skin or your internal organs are moving around.
- Olfactory (smell) hallucinations: These hallucinations involve experiencing smells that don’t exist or that no one else can smell.
- Gustatory (taste) hallucinations: These hallucinations cause tastes that are often strange or unpleasant. Gustatory hallucinations (often with a metallic taste) are a relatively common symptom for people with epilepsy.
- Presence hallucinations: These hallucinations make you feel that someone is in the room with you or standing behind you.
- Proprioceptive hallucinations: These hallucinations make you think that your body is moving, such as flying or floating, when it’s not.
There are also types of hallucinations that are sleep-related, including:
- Hypnopompic hallucinations: These are hallucinations that occur as you're waking up from sleep. For most people, hypnopompic hallucinations are considered normal and aren’t cause for concern. They may be more common in people with certain sleep disorders.
- Hypnagogic hallucinations: These are hallucinations that happen as you're falling asleep. They’re usually short-lasting and about 86% of them are visual. People commonly see moving patterns and shapes or vivid images of faces, animals or scenes. These hallucinations aren’t usually a cause for concern.
What is the difference between a hallucination and a delusion?
A hallucination is a sensory experience. It involves seeing, hearing, tasting, smelling or feeling something that isn't there.
Delusions are unshakable beliefs in something untrue. For example, they can involve someone thinking they have special powers or they’re being poisoned despite strong evidence that these beliefs aren’t true.
What’s the difference between a hallucination and an illusion?
Hallucinations are a perception not based on sensory input, whereas illusions are misinterpretations of sensory inputs. In other words, hallucinations involve experiencing something that doesn’t exist.
Illusions happen when you misinterpret something real in your environment.
For example, you might mistake a black bag sitting on a window sill for a black cat. Upon further examination, you realize that it’s a bag and not a cat. This is an illusion.
How do I know if I'm hallucinating?
It’s possible to experience hallucinations while being aware that they aren't real.
For example, some people grieving the death of a loved one may momentarily hear their deceased loved one’s voice or see them, but they know that what they’re hearing or seeing is impossible. Most people are also able to tell that the hallucinations that happen when they’re falling asleep or waking up aren’t real.
In these cases, you can use context clues and your environment to tell that what you’re “experiencing” isn’t real.
However, some people don’t realize that they’re hallucinating. This is more common in chronic conditions like schizophrenia and dementia.
What are the possible causes of hallucinations?
There are many possible causes of hallucinations, including:
- Temporary causes.
- Certain mental health conditions.
- Certain neurological conditions.
- Side effects of certain medications.
Temporary causes of hallucinations
The following conditions or situations may temporarily cause hallucinations:
- Falling asleep or waking up.
- Being under the influence of alcohol or certain drugs, such as marijuana, hallucinogens (LSD and PCP) cocaine, amphetamines, heroin or ketamine.
- High fever, especially in children and older people.
- Severe dehydration.
- Sleep deprivation.
- Severe pain.
- Infections like UTIs, especially in older people.
- Recovering from anesthesia after a surgery or procedure.
Experiencing hallucinations in these ways is usually not a cause for concern. However, if you have an acute medical issue that’s causing them, like an infection or a fever, it’s important to seek medical treatment for the issue.
Mental health conditions that may cause hallucinations
Schizophrenia is the main mental health condition that causes hallucinations. Schizophrenia refers to both a single condition and a spectrum of conditions that fall under the category of psychosis-related disorders. These are conditions where a person experiences some form of “disconnection” from reality (psychosis), which can include hallucinations.
Conditions that fall under the schizophrenia spectrum and may cause hallucinations include:
- Schizotypal personality disorder (which also falls under the category of personality disorders).
- Delusional disorder.
- Brief psychotic disorder.
- Schizophreniform disorder.
- Schizoaffective disorder.
Hearing voices is the most common type of hallucination in people with these mental health conditions.
Other mental health conditions that may cause hallucinations include:
- Bipolar disorder: People with bipolar disorder can experience hallucinations during both severe depressive or severe manic episodes.
- Major depression with psychotic features (psychotic depression): Major depressive disorder (MDD) with psychotic features is a distinct type of depressive illness in which mood disturbance is accompanied by either delusions, hallucinations or both.
Neurological conditions that may cause hallucinations
Neurological conditions that may cause hallucinations include:
- Parkinson’s disease: This condition causes a part of your brain to deteriorate, causing more severe symptoms over time. About 20% to 40% of people with Parkinson’s disease experience hallucinations or delusions. This can also be due to side effects of medications or dementia.
- Alzheimer’s disease: About 13% of people with Alzheimer’s disease experience hallucinations. Hallucinations are caused by changes within your brain that result from the condition.
- Lewy body dementia: This condition involves the buildup of clumps of proteins — called Lewy bodies — in your brain’s nerve cells. Lewy bodies damage nerve cells. It can cause hallucinations, and they’re usually visual. They might be one of the first signs of Lewy body dementia.
- Epilepsy: People who have epilepsy that involves a part of their brain called the temporal lobe can experience hallucinations — most commonly olfactory hallucinations.
- Narcolepsy: This is a neurological disorder that affects your brain’s ability to control sleep and wakefulness. People with narcolepsy often experience hallucinations just before falling asleep (hypnagogic hallucinations) or just after waking up (hypnopompic hallucinations).
Other conditions that can cause hallucinations
Charles Bonnet syndrome causes a person whose vision has started to deteriorate to see hallucinations. This condition only causes visual hallucinations.
Terminal illnesses, including liver failure, kidney failure, stage 3 HIV/AIDS and brain cancer can all cause hallucinations.
Medications that can cause hallucinations
Many prescription medications can occasionally cause or worsen hallucinations as a side effect. Elderly people may be at greater risk due to increased sensitivity to medications. Hallucinations caused by medications may be dose-related and usually stop when you discontinue the medication. Your healthcare provider is the best source of information about medication side effects. Never stop taking a medication without speaking to your healthcare provider first.
Care and Treatment
How are hallucinations treated?
The treatment for hallucinations depends on the cause. Hallucinations caused by temporary conditions, such as high fever, severe dehydration or infection, will resolve once the underlying condition has been treated.
Certain medications and therapies may help treat hallucinations in people with chronic conditions that cause them, including:
- Typical (first-generation) and atypical (second-generation) antipsychotic medications may help decrease the frequency and severity of hallucinations in people with schizophrenia spectrum disorders, bipolar disorder and major depressive disorder with psychotic features.
- Repetitive transcranial magnetic stimulation (rTMS) may reduce auditory hallucinations that don’t respond to antipsychotic medications.
- Acetylcholinesterase inhibitors may reduce psychosis (hallucinations and/or delusions) in people with Alzheimer’s disease, Parkinson’s disease and Lewy body dementia. Acetylcholinesterase inhibitors are a group of drugs that block the normal breakdown of acetylcholine, which is a neurotransmitter that functions in both the peripheral nervous system and central nervous system.
Can hallucinations be prevented?
While not all hallucinations can be prevented, there are some strategies you can use at home that might help reduce the frequency of them for certain people with neurological conditions that may cause hallucinations, including:
- Having good lighting and participating in stimulating activities in the evening.
- Checking for sounds that might be misinterpreted, like noise from a television or an appliance.
- Looking for and correcting lighting that casts shadows, reflections or distortions.
- Covering mirrors with a cloth or removing them if the person thinks they’re looking at a stranger.
If you’re taking medication to help treat hallucinations, it’s important to continue taking the medication unless your healthcare provider tells you otherwise. Stopping the medication suddenly can cause more intense hallucinations.
How can I help someone who is experiencing a hallucination?
If you’re with someone who’s experiencing a hallucination, there are some steps you should take:
- Assess the situation and determine if the hallucination is a problem for the person or you. If the hallucination upsets them or leads them to do something dangerous, react calmly and quickly with reassuring words and a comforting touch.
- Don’t argue with the person about what they’re experiencing. If their behavior in response to their hallucination isn’t dangerous, you may not need to intervene.
- Avoid trying to reason with the person experiencing a hallucination. You can say you don’t see what your loved one is seeing, but some people find it more calming to acknowledge what the person is seeing to minimize stress. For example, if the person sees a dog in the room, it may be more helpful to say, "I’ll take the dog out," rather than arguing that there’s no dog.
When to Call the Doctor
When should I see my healthcare provider about hallucinations?
If you or someone you know is experiencing hallucinations and is detached from reality, you or they should get checked by a healthcare provider as soon as possible.
Many medical and mental health conditions that can cause hallucinations may quickly become emergencies. The person experiencing hallucinations shouldn’t be left alone.
A note from Cleveland Clinic
It’s important for people experiencing hallucinations to talk about them with their family and healthcare team. Hallucinations are manageable with treatment and can become disturbing or dangerous if they’re not treated. Discuss all possible symptoms with your healthcare provider, no matter how minor or bizarre you may think they are. Hallucinations can make you feel nervous, paranoid and frightened, so it's important to be with and talk with someone you can trust.
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