Hallucinations can be a sign of a mental health illness, but they do not always mean a person is unwell. Hallucinations are, in fact, relatively common.

One 2015 study from Europe found that 7.3 percent of people reported a life-long experience of hearing voices. A further study from South Africa on hallucinations in the general population put the rate higher at 12.7%.

Scientists do not fully understand why some people have hallucinations, and others do not. Neither do they know what triggers hallucinations in people with conditions such as schizophrenia.

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Hallucinations are not always a sign of a mental health disorder.

Hallucinations can happen any time there is a change in brain activity. For example, some people are more vulnerable to hallucinations when they are falling asleep or partially waking.

A 2019 study in mice that took a hallucinogenic drug found that the animals had less activity in brain regions that the researchers associated with managing incoming visual information.

This observation suggests that a hallucination could be the brain’s way of compensating for a drop in sensory information.

There are many different types of hallucinations, including:

  • Auditory hallucinations: These are when someone hears something that is not there, such as a voice or radio.
  • Visual hallucinations: These cause someone to see something that is not real, such as a person or animal.
  • Olfactory hallucinations: These can occur when a person smells something that is not there.
  • Gustatory hallucinations: These cause someone to taste something they did not eat.
  • Tactile hallucinations: These occur when a person feels like something or someone touched them.
  • Somatic hallucinations: These hallucinations can affect the entire body, causing unreal sensations such as that of bugs crawling on the skin.

Learn more about what happens in the brain during a hallucination.

Numerous medical conditions and other factors can cause hallucinations. A 2010 study attempted to review and discuss many of these hallucinations and their causes. They include:


Drugs called hallucinogens can induce hallucinations. These drugs temporarily change the way the brain processes and sends information, causing unusual experiences and thoughts.

LSD, salvia, dimethyltryptamine (DMT), and certain mushrooms are common hallucinogens.


Schizophrenia is a mental health condition that changes the way a person thinks and behaves. It can also cause psychosis, which is a loss of being in touch with reality.

People with psychosis may experience delusions and hallucinations and exhibit behaviors that are not typical. Antipsychotic medication may help manage symptoms, and some people function better with therapy.

Postpartum mental health disorders

Many new parents struggle with postpartum depression and anxiety. Less commonly, some experience postpartum psychosis, which can cause hallucinations.

An example is if a mother believes she is hearing her baby crying when the baby is not doing so. In more extreme cases, a mother may hear a voice telling her to kill her child.

Because postpartum psychosis can endanger the baby and disrupt the relationship between parent and child, prompt treatment is vital. Therapy, medication, and social support can help.

Anxiety and depression

People with anxiety and depression may experience periodic hallucinations. The hallucinations are typically very brief and often relate to the specific emotions the person is feeling. For example, a depressed person may hallucinate that someone is telling them they are worthless.

Treating the underlying disorder can often eliminate these hallucinations.

Learn more about psychosis in depression.

Alcohol withdrawal

Withdrawal from alcohol can cause hallucinations, especially in people who experience a severe withdrawal syndrome called delirium tremens.

A person with delirium tremens may also become very sick, vomit, or shake. Symptoms usually disappear after several days.

Dementia and other brain disorders

Dementia progressively damages the brain, including regions involved with sensory processing. People in mid to late stage dementia may experience auditory and visual hallucinations.

Sometimes, they see people who have died. In other cases, their hallucinations may be terrifying and can trigger feelings of paranoia and panic that make it difficult for them to trust caregivers.

Medication may help ease these symptoms.


Sometimes hallucinations are a symptom of a seizure disorder. A person may experience hallucinations during or after a seizure. In most cases, treating the seizures prevents the hallucinations.


Some people with migraines experience hallucinations during or right before a migraine. These hallucinations are often visual. A person might see spots and colors that are not there or other unusual images.

Sleep disorders

Some people experience hallucinations that doctors associate with sleep disorders. The hallucinations commonly appear as a person falls asleep or wakes.

In some cases, the hallucination occurs with an episode of sleep paralysis, which happens when a person wakes up and is temporarily unable to move.

Treating sleep disorders may help ease symptoms. In some cases, knowing that the hallucinations happen because of brain changes during the sleep cycle can make them less frightening.

Sensory diseases

People with hearing or vision loss may experience hallucinations. This may be due to brain changes in sensory processing regions or in the visual or auditory information the brain receives.

Other causes

In some cases, hallucinations may not relate to an illness or drugs. Sometimes, suggestive forces trigger the hallucination.

For example, in religious traditions, where hearing the voice of God is common, a person might report an auditory hallucination. A person sleeping in a house they believe to be haunted might hear noises or see ghostly figures due to heightened anxiety.

A hallucination is not a delusion, though the two are closely related. A delusion is a false belief, while a hallucination is a false perception.

Many people may have fallen for optical illusions and other mental tricks. However, a hallucination is more than an error in perception.

People experiencing hallucinations see or hear things that are not actually present, and that do not match the experiences of others around them.

They may also believe in the realness of their hallucinations or attach specific meaning and false beliefs to them. These attached false beliefs are delusions.

Other symptoms of hallucinations

Hallucinations often signal an underlying problem with how the brain is processing information, such as when a person with dementia develops hallucinations or depression triggers psychosis.

Some other symptoms a person might experience with hallucinations include:

  • changes in brain function as a person ages
  • unusual beliefs
  • depression or anxiety
  • visual or hearing problems
  • paranoid or aggressive behavior
  • belief in conspiracies
  • seizures
  • headaches

It is sensible to see a doctor following any hallucination, even if there are no other symptoms. It is particularly important to seek medical care if someone with an illness that may cause hallucinations experiences worsening hallucinations or other changes in mood or behavior.

Not all hallucinations require treatment, especially if the hallucination is a singular event. A hallucination is not a medical emergency, but only a doctor can determine whether it signals a serious health issue.

Hallucinations are more common than many people might realize. Although they can be frightening, they do not always mean a person has a serious brain disorder or mental health issue.

People with hallucinations and those who love them should track symptoms to measure when the hallucinations happen and whether anything seems to trigger them. This record-keeping can help a doctor better treat their symptoms.