Can Parkinson’s Disease Cause Hallucinations?

Medically reviewed by Seunggu Han, MD on October 10, 2017Written by Jacquelyn Cafasso

Hallucinations and delusions are possible complications of Parkinson's disease (PD). They are often referred to as PD psychosis. Hallucinations are when someone experiences something that isn’t there. Hallucinations can be:

  • seen (visual)
  • heard (auditory)
  • smelled (olfactory)
  • felt (tactile)
  • tasted (gustatory)

Delusions are views that aren’t based in reality. One example is paranoia that persists even when a person is presented with contrary evidence.

Hallucinations during PD can be frightening and debilitating. There are many factors that can contribute to hallucinations in people with PD. But the majority of cases occur as side effects of PD medications.

The connection between Parkinson’s disease and hallucinations

Hallucinations and delusions in people with PD is often referred to as Parkinson’s disease psychosis. Psychosis is fairly common in people with PD, especially those in later stages of the illness. It’s estimated to occur in up to 50 percent of people with PD.

Research shows that psychotic symptoms are related to high levels of a neurotransmitter known as dopamine. This is often a result of medications. However, the reason why some people with PD experience psychosis while others don’t isn’t quite understood.

What causes hallucinations and delusions?

There are several reasons why someone with PD might experience delusions or hallucinations.

Medications

People with Parkinson’s disease often have to take several different medications. These medications help treat the PD and other illnesses associated with old-age. However, these medications have many side effects.

Taking drugs that affect the dopaminergic receptors is a significant risk factor. This is because some PD medications increase dopamine levels. High levels of dopamine cause hallucinations and other emotional symptoms in people with PD.

Drugs that may contribute to hallucinations or delusions in people with PD include:

Dementia

Chemical and physical changes in the brain can contribute to hallucinations and delusions. This is often seen in cases of dementia with Lewy bodies. Lewy bodies are abnormal deposits of a protein called alpha-synuclein.

This protein builds up in areas of the brain that control:

  • behavior
  • cognition
  • movement

One symptom is having complex and detailed visual hallucinations.

Delirium

A change in a person’s concentration or awareness causes delirium. There are many situations that can trigger a temporary episode of delirium. People with PD are sensitive to these changes. These can include:

  • a change in environment or an unfamiliar location
  • infections
  • electrolyte imbalances
  • fever
  • vitamin deficiencies
  • a fall or head injury
  • pain
  • dehydration
  • hearing impairment

Depression

Depression among people with Parkinson’s disease is quite common. More than 50 percent of people with PD will experience depression. The trauma of a PD diagnosis can take a toll on a person’s mental and emotional health. People with major depression can also have symptoms of psychosis, including hallucinations. This is called psychotic depression.

People with PD who are depressed may abuse alcohol or illegal drugs. This could also trigger episodes of psychosis.

What treatments are available for Parkinson’s psychosis?

Your doctor may first reduce or change the PD medication you’re taking to see if that reduces psychotic symptoms. This is about finding a balance. People with PD need higher dopamine levels to help control motor symptoms. But dopamine levels can’t be so high that they cause hallucinations and delusions.

Your doctor might consider prescribing an antipsychotic drug if reducing your PD medication doesn’t help.

Antipsychotic drugs should be used with extreme caution in people with PD. They may cause serious side effects and can even make hallucinations and delusions worse.

Common antipsychotic drugs like olanzapine (Zyprexa) might improve hallucinations, but often result in worsening PD motor symptoms. Clozapine (Clozaril) and quetiapine (Seroquel) are two other antipsychotic drugs that are often prescribed at low doses to treat PD psychosis. However, there are still concerns about their safety and efficacy in PD patients.

In 2016, the U.S. Food and Drug Administration (FDA) approved the first medication — pimavanserin (NuPlazid) — specifically for use in PD psychosis. In clinical studies, pimavanserin was shown to decrease the frequency and severity of hallucinations and delusions without worsening the primary motor symptoms of PD. The drug shouldn’t be used in people with dementia-related psychosis due to an increased risk of death.

Antidepressants can be used to treat depression in people with PD. The most commonly used antidepressants are selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac).

Psychotic symptoms caused by delirium may improve once the underlying condition is treated.

What to do if someone is having hallucinations or delusions

Arguing with someone experiencing hallucinations or delusions is rarely helpful. The best you can do is to try to remain calm and acknowledge the person’s thoughts. The goal is to reduce their stress and keep them from becoming frantic.

Psychosis is a serious condition and may lead a person to harm themselves or others. Most hallucinations in people with PD are visual, and they usually aren’t life-threatening.

Another way to help is to take notes on the person’s symptoms, such as what they were doing before the hallucinations or delusions started, and what kinds of images they claimed to experience. Then you can pass this information along to their doctor. People with PD psychosis tend to remain silent about experiences like this, but it’s essential that their treatment team understands the full range of their symptoms.

The takeaway

It’s important to know that experiencing hallucinations or delusions caused by Parkinson’s disease doesn’t mean that a person has a psychiatric illness, like schizophrenia. Most of the time, PD psychosis is a side effect of certain PD medications.

Speak to your doctor if you experience hallucinations. If psychotic symptoms don’t improve or go away with a change in medication, your doctor may prescribe an antipsychotic drug, such as newly approved pimavanserin.

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