Psychosis doesn’t just affect individuals with psychiatric disorders such as schizophrenia. It also affects other illnesses, including Parkinson’s disease (PD), a degenerative disorder that disturbs movement and balance.

Over five million people worldwide have PD, struggling with symptoms such as shaking, stiffness, slowness of movement and instability.

“Psychosis in Parkinson’s disease is very common,” according to Michael S. Okun, M.D., national medical director at the National Parkinson Foundation and author of the Amazon no. 1 bestseller Parkinson’s Treatment: 10 Secrets to a Happier Life.

In fact, psychosis may affect 1 in 5 Parkinson’s patients, he said. And as many as 2 out of 3 patients may experience minor symptoms, “such as non-bothersome visual illusions.” (An example is “seeing something in the corner of your eye that may not be there, [such as] a bug in the sink for an instant.”)

“Patients primarily experience visual hallucinations,” said James Beck, Ph.D, the director of research programs at Parkinson’s Disease Foundation. A smaller number of patients — 10 to 20 percent — experience auditory hallucinations, he said.

Some patients also may experience delusions, or fixed false beliefs. According to Dr. Okun in his piece on managing psychosis in PD:

“Delusions are usually of a common theme, typically of spousal infidelity. Other themes are often paranoid in nature (such as thinking that people are out to steal from one’s belongings, or to harm or place poison on their food, or substitute their Parkinson medications, etc.) Because they are paranoid in nature, they can be more threatening and more immediate action is often necessary, compared to visual hallucinations (Zahodne and Fernandez 2008a; Zahodne and Fernandez 2008b; Fernandez 2008; Fernandez et al. 2008; Friedman and Fernandez 2000). It is not uncommon that patients actually call 9-1-1 or the police to report a burglary or a plot to hurt them.”

In the early stages of psychosis, patients tend to have insight into their symptoms, Beck said. In other words, they realize that what they’re seeing (or hearing) isn’t actually there. But this may worsen over time. According to Okun in the same piece:

“At later stages [of psychosis], patients may be confused and have impaired reality testing; that is, they are unable to distinguish personal, subjective experiences from the reality of the external world. Psychosis in Parkinson’s disease patients frequently occurs initially in the evening, then later on spills into the rest of the day.”

Psychosis typically doesn’t develop until several years after a person has been diagnosed with PD, Beck said.

(If hallucinations are present from the start, then it may be another condition. For instance, Lewy body dementia “might cause psychosis and can be misdiagnosed as Parkinson’s disease.”)

These symptoms can be incredibly disturbing for both patients and caregivers, Beck said. They also make caregiving more challenging and overwhelming. Some research has found that hallucinations were the strongest predictor for institutionalization.

“There are many potential triggers for hallucinations or other psychotic phenomena and these include medications, infections and sleep deprivation,” Okun said. Particularly in the elderly population, stress, dehydration and urinary tract infections can spark hallucinations, Beck said.

Medications that treat Parkinson’s disease increase levels of dopamine in the brain. This is important, because the disorder involves the malfunction and loss of neurons that produce dopamine. Dopamine relays messages to the substantia nigra and other parts of the brain, which control movement and coordination.

But dopamine also plays a pivotal role in hallucinations, Beck said. In other words, by boosting dopamine levels, these medications improve motor symptoms, and may produce psychosis.

Parkinson’s disease itself may lead to hallucinations. As the disease progresses, it can impair cognition and visual processing, leading to dementia, Beck said.

Treating psychosis in people with Parkinson’s is usually done with medications.

“Psychosis does not always require treatment, particularly if hallucinations are non-bothersome,” Okun said. If it does require treatment, doctors try to pinpoint what’s causing the hallucinations. For instance, if it’s an infection, they may prescribe antibiotics. If it’s a sleep disorder, they may prescribe a sleeping aid.

To reduce hallucinations directly, atypical antipsychotics, such as clozapine (Clozaril) and quetiapine (Seroquel), may be used, Okun said.

To date clozapine is the only medication shown to be effective in double-blind studies, Beck said. (This 2011 paper reviews the research for clozapine along other medications.) “Though given at very low doses for Parkinson’s, clozapine may cause a dangerous drop in white blood cell count. Therefore, patients must undergo regular blood monitoring.”

First-generation or typical antipsychotic drugs, such as haloperidol, are not prescribed for psychosis in PD. In fact, this is actually dangerous, because these drugs lower dopamine and can induce a “neuroleptic crisis,” Beck said.

Nuplazid to Treat Hallucinations in Parkinson’s

Beck also mentioned a newer drug called pimavanserin (Nuplazid), developed specifically for psychosis in Parkinson’s disease. Instead of modulating dopamine, this drug targets serotonin.

Some research has suggested that activating particular serotonin receptors can lead to visual hallucinations. “Shutting down the activity of this receptor and neurons associated with it may alleviate hallucinations [without] impacting motor performance,” noted Beck.

Nuplazid is currently the only medication approved by the U.S. Food and Drug Administration (FDA) for the treatment of hallucinations and delusions associated with Parkinson’s disease psychosis. Since its approval, it has become the go-to choice for many physicians treating people with Parkinson’s who are dealing with hallucinations.

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Psychosis is a serious problem for many patients with Parkinson’s disease. Beck stressed the importance of telling your doctor right away if you’re struggling with hallucinations or other psychotic symptoms. “Early intervention [or] treatment can make a difference, improving quality of life for both the person with PD and their caregiver.” He also encouraged readers to work with a movement disorders specialist, who will have expertise in both motor and non-motor symptoms.

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