Hallucinations: Definition, Causes, Treatment & Types (2024)

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.