Parkinson’s disease most commonly causes tremors, stiffness, and difficulties moving, but the condition can also cause hallucinations.

Hallucinations affect the senses and can result in people seeing, hearing, feeling, smelling, and tasting things that are not real.

Up to 40% of people with Parkinson’s disease experience hallucinations or delusions, and this number increases as the condition progresses. Doctors refer to the symptoms as Parkinson’s disease-associated psychosis.

Hallucinations can occur as a side effect of medications, but they may also be a Parkinson’s disease symptom or point to another issue, such as dementia.

Keep reading to learn more about Parkinson’s disease hallucinations, including the causes, treatment options, and outlook.

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Hallucinations can affect any sense. They involve seeing, hearing, feeling, smelling, or tasting something that is not actually there. They happen when an individual is awake.

There are different types of hallucinations that people with Parkinson’s disease may experience. These are:

  • Visual: People with Parkinson’s disease typically have visual hallucinations, such as seeing animals or people who are not really there.
  • Auditory: A small number of those with Parkinson’s disease may hear voices or sounds that are not real.
  • Olfactory: It is rare for someone with Parkinson’s disease to smell a scent unrelated to a source.
  • Tactile: The sensation of something touching the skin is also uncommon in Parkinson’s disease.
  • Gustatory: Tasting an unusual flavor in the mouth is uncommon in Parkinson’s disease as well.

Learn more about hallucinations here.

Delusions

Delusions are less common than hallucinations, affecting around 8% of those with Parkinson’s disease. They are more common in advanced Parkinson’s disease.

Delusions are thoughts, beliefs, or worries that are not based on reality and that are unusual for the person. They may be more complicated and challenging to treat than hallucinations.

Although an individual can have delusions about anything, there are some common themes in Parkinson’s disease-associated psychosis. These include:

  • Jealousy: The individual may believe that a friend or partner is unfaithful and act paranoid, upset, or suspicious.
  • Persecutory and paranoia: The person may feel attacked and harassed and that someone is out to get them or harm them. They may act paranoid, suspicious, or withdrawn.
  • Somatic: The individual may become obsessed with their body or health and believe that their body is unusual. They may visit their doctor frequently and be highly concerned about symptoms.

Delusions of jealousy and persecution are the most widespread in people with Parkinson’s disease, and they can sometimes lead to aggression that may pose a safety risk to the individual’s family and caregivers.

Additionally, those experiencing paranoia may refuse to take their medications, as they believe them to be poisonous.

For these reasons, caregivers may need outside assistance when caring for a loved one who is experiencing delusions.

There are three primary reasons that an individual may develop psychosis in Parkinson’s disease. These are:

  • medication use
  • dementia
  • delirium

The sections below look at each of these reasons in more detail.

Medication use

Various medications that doctors prescribe to treat Parkinson’s disease can lead to temporary psychosis.

The traditional Parkinson’s disease medications, including carbidopa-levodopa (Sinemet) and dopamine agonists, boost dopamine supply. Although this can improve an individual’s motor symptoms, it may also cause emotional and behavioral changes.

Additionally, other Parkinson’s disease medications — such as amantadine and anticholinergics — may affect dopamine balance by reducing levels of the neurotransmitter acetylcholine.

Dementia

If a person has had Parkinson’s disease for at least a year and experiences a decline in thinking and reasoning, a doctor may diagnose Parkinson’s disease dementia.

Parkinson’s disease initially affects the areas of the brain involved in movement. However, as the chemical and physical changes spread, the condition can affect a person’s mental function and contribute to hallucinations.

A fundamental change in Parkinson’s dementia is developing unusual deposits of a protein called alpha-synuclein in the brain. These are known as Lewy bodies, after the neurologist who discovered them.

Delirium

Delirium may cause a temporary and reversible change in a person’s behavior and consciousness that can cause hallucinations. It typically develops quickly, sometimes in just hours, and it may resolve after a doctor treats the underlying condition.

Some possible causes of delirium include:

People with Parkinson’s disease are particularly sensitive to change, and various situations can trigger delirium. These may include staying in the hospital and having new surroundings.

Risk factors for Parkinson’s disease hallucinations

Certain factors can increase the risk of developing Parkinson’s disease hallucinations. These may include:

  • dementia
  • sleep disorders
  • impaired vision
  • increasing age
  • advanced Parkinson’s disease
  • use of Parkinson’s disease medications

Depression also increases an individual’s risk of experiencing hallucinations. This mental health condition is common, affecting around 50% of people with Parkinson’s disease. This is potentially due to the challenges that Parkinson’s disease presents.

Depression can lead to psychosis symptoms, including hallucinations. Individuals may also misuse alcohol or other substances in an attempt to cope with the challenges of living with a chronic condition. This can, in turn, trigger psychosis episodes.

If a person is experiencing hallucinations and delusions, they should contact a doctor as soon as possible to prevent the condition from worsening.

Because Parkinson’s disease medications can cause hallucinations, a doctor may recommend some changes to balance the person’s dopamine levels. For example, they may reduce the dosage of their medication or change the prescription.

If this approach does not ease the individual’s hallucinations, the doctor may recommend an antipsychotic drug to address unusual chemical levels in the brain. However, these medications require caution, as they may worsen symptoms and hallucinations.

Doctors currently consider three antipsychotic medications for those with Parkinson’s disease. These are:

  • clozapine (Clozaril)
  • quetiapine (Seroquel)
  • pimavanserin (NuPlazid)

In 2016, pimavanserin became the first medication specifically approved for Parkinson’s disease-associated psychosis. Some studies suggest that it can decrease the frequency and severity of hallucinations without worsening a person’s motor symptoms.

Parkinson’s disease in itself does not lead to death. However, the condition can negatively impact an individual’s body, putting them at greater risk of severe infections and, therefore, affecting their outlook.

If a person develops dementia and experiencing symptoms such as hallucinations and delusions, it increases the risk of hospitalization and death. A 2010 study notes that this group of people was around 50% more likely to die prematurely than individuals without these symptoms.

When doctors treat Parkinson’s disease-associated psychosis early on, it may help increase an individual’s life expectancy.

Many people with Parkinson’s disease experience hallucinations, delusions, or both, which are known collectively as psychosis.

Having hallucinations means that the individual may see or hear things that are not real. Rarely, people may also feel, smell, or taste things that do not exist. Typically, this is a side effect of Parkinson’s disease medications, but it can also be due to other medical conditions, including dementia.

If an individual is experiencing symptoms of Parkinson’s disease-associated psychosis, they should seek a doctor’s advice at the earliest opportunity. Receiving timely treatment can help improve their outlook. The doctor can alter their treatment, and they may prescribe antipsychotic medication.