Parkinson’s psychosis: What it is and why it happens

Last updated Sept. 16, 2024, by Lindsey Shapiro, PhD
Fact-checked by Ana de Barros, PhD

More than half of people with Parkinson’s disease will at some point develop psychosis, a collection of symptoms in which a person has trouble distinguishing what is or isn’t real.

While Parkinson’s may be best known for its hallmark motor symptoms, it can also lead to nonmotor symptoms including changes in mood, thinking, and behavior. For this reason, psychosis might take people with the disease and their families by surprise, and can be one of the more unsettling symptoms of the neurodegenerative disease.

Psychosis can cause feelings of fear, embarrassment, or distress that make it more difficult to talk about with a healthcare professional. But there are ways to manage Parkinson’s psychosis, so the sooner your doctor knows about it, the easier it will be to come up with a treatment plan to help stop or minimize its effects on your daily life.

What is Parkinson’s psychosis?

Psychosis means a loss of contact with reality; Parkinson’s disease psychosis refers specifically to symptoms of psychosis that occur when there’s already an established Parkinson’s diagnosis.

While psychosis is sometimes considered its own psychiatric condition, Parkinson’s psychosis is generally thought of as a symptom of a medical condition, occurring secondarily to brain changes related to the disease or medications taken to manage it.

Parkinson’s psychosis can range from mild illusions or misperception of things in one’s environment, to full-blown hallucinations (perceiving things that aren’t there), or delusions (beliefs not based in reality).

Not all people with Parkinson’s develop psychosis, but different studies estimate that 25%-70% of those with Parkinson’s may experience it in some form over the course of their disease, with 20%-40% experiencing hallucinations or delusions.

Common symptoms

Parkinson’s psychosis affects people in different ways. Some may develop signs of psychosis in the first few years of living with the disease, while others may live decades before noticing any symptoms. Still, the likelihood of having psychosis increases in later disease stages.

Parkinson’s psychosis symptoms also may increase in severity over time, and in fact, are sometimes considered to exist on a spectrum.

In the period before psychosis emerges, you might experience vivid dreams and nightmares. Over time, it may progress to minor illusions that ultimately give way to hallucination or delusions, although not everyone will progress through these stages in the same way. Symptoms of psychosis also may emerge or get worse during illness or hospitalizations, or when in unfamiliar environments.

Hallucinations

Hallucinations involve seeing, hearing, sensing, or otherwise experiencing things that do not exist. It also has been described as the brain playing tricks on any of the body’s five senses, with visual hallucinations, such as seeing an animal or person, by far being the most common type. Hallucinations are not dreams or nightmares; they can happen at any time of day or night that a person is awake.

This is the most common manifestation of Parkinson’s psychosis, occurring in around 25%-35% of people in mid- to advanced- stage disease, and more than half of those who have Parkinson’s disease dementia, a group of symptoms associated with a decline in memory and thinking.

Other types of hallucinations also can occur, although less commonly, including:

• auditory, in which the person hears sounds or voices that aren’t there
• tactile, where the person feels sensations that aren’t real, such as the sensation of something touching or crawling on the skin
• olfactory, when the person experiences phantom smells that don’t have a real source
• gustatory, in which one perceives tastes without an actual source.

Some people who experience hallucinations know they are not real, which is called retaining insight. But for others, hallucinations feel real.

As Parkinson’s disease progresses, the ability to retain insight may be lost. Once that happens, a person may start trying to interact with the perceived beings or objects in their environment.

Most hallucinations caused by Parkinson’s psychosis are short and nonthreatening, but in some cases, prolonged hallucinations can become bothersome or dangerous.

Illusions

At the onset of psychosis, you may experience what’s known as minor hallucinations, which are most often visual. It can include illusions, or brief misperceptions of real things in the environment, for example, momentarily imagining clothes hanging in the closet as being people.

Minor hallucinations also can manifest as a “sense of presence,” or a false feeling that a person or animal is nearby, or as “passage hallucinations,” when you see an unformed object move in your peripheral vision.

For some people, minor hallucinations advance to full-blown hallucinations, becoming more vivid, clear, and detailed.

Delusions

Delusions are illogical or irrational views not based on reality. They are not as common as hallucinations, occurring in fewer than 10% of those with Parkinson’s, and are more challenging to manage.

Delusions can be linked to certain medications, but they may also result from the overall worsening of the condition.

There are three general categories of delusions:

• persecution, such as fearing of being poisoned by medication or food
• jealousy, such as making accusations of marital infidelity
• somatic, such as believing the body is functioning abnormally.

At first, delusions may appear as generalized confusion at night, which over time evolves into clear delusions occurring at any time of day.

Delusions feel very real to people. If the nature of the delusion makes them feel threatened, they may become very argumentative, paranoic, aggressive, defiant, or agitated. They also may become socially withdrawn, anxious, or suspicious and refuse to take necessary medications.

For this reason, delusions are more likely than hallucinations to be distressing and cause unsafe behavior.

Causes of Parkinson’s psychosis

Parkinson’s disease is characterized by the loss of nerve cells that produce dopamine, an important brain-signaling chemical, or neurotransmitter.

Previously, Parkinson’s psychosis was believed to arise solely as a side effect of standard Parkinson’s therapies that aimed to increase dopamine levels, but scientists now understand this is likely only one part of a complex mix of factors.

Structural and neurochemical changes from the neurodegenerative disease itself are also among the causes of Parkinson’s psychosis, with up to 70% of those with Parkinson’s experiencing it throughout the course of their disease.

Parkinson’s medications

Standard treatments for Parkinson’s try to increase dopamine signaling in the brain. While this helps to relieve Parkinson’s motor symptoms, elevated dopamine levels can alter brain activity in ways that lead to hallucinations or delusions.

The goal of treatment is to find a balance where motor symptoms are controlled but dopamine-associated side effects are minimized. If the dose of these medications is not right, it can lead to psychosis.

Other Parkinson’s medications try to block the activity of a neurotransmitter called acetylcholine, which is involved in movement control. These medications are largely used to manage tremors or uncontrollable muscle contractions. As with dopaminergic medications, brain-signaling changes with these therapies and a disrupted dopamine acetylcholine balance also can cause confusion or hallucinations.

Disease-related brain changes

Physical and chemical changes that occur in the brain as Parkinson’s progresses can contribute to psychosis, but these factors are not precisely understood. This is commonly observed in cases of Parkinson’s with dementia.

Scientists are still trying to better understand the brain alterations that drive psychosis in Parkinson’s, but some may include:

• damage or dysfunction in brain areas or circuits involved in cognition, vision, or other sensory perceptions; for visual hallucinations in particular, dysregulation of parts of the brain involved in visual processing may contribute
• neurochemical alterations, as the brain works best with a good balance of several neurotransmitters; beyond dopamine, neurotransmitters including serotonin and acetylcholine are dysregulated in Parkinson’s, and may contribute to psychosis by altering normal brain networks
• sleep disturbances, as brain signaling networks during dreaming could cause imagery to be absorbed and the brain is unable to distinguish that it’s not reality later on.

Delirium

In some cases, certain medications or illnesses can cause delirium, where psychotic symptoms come on quickly and go away when the triggering factor is managed. This also can cause existing psychosis to get temporarily worse.

Risk factors

Not all people with Parkinson’s develop psychosis. A number of possible risk factors for this nonmotor symptom have been identified which include:

• dementia and memory impairments
• depression or anxiety
• sleep disorders, including REM sleep behavior disorder, vivid dreaming, and sleep apnea
• vision problems
• older age
• advanced or progressing Parkinson’s
• exposure to Parkinson’s medications
• new or changing medications.

Certain medical conditions also can trigger the onset of psychosis or increase the severity of symptoms, including:

• infection associated with fever
• dehydration
• imbalanced nutrition
• psychosocial stress
• anemia
• thyroid problems
• low levels of certain vitamins.

Diagnosis

If a person with Parkinson’s or their caregiver suspects there are signs of psychosis, it is important to see a healthcare professional as soon as possible to get a diagnosis and start on the appropriate treatment.

Because psychosis may start off mild and progress over time, it isn’t always easy to catch it right away. Possible early warning signs of psychosis may include vivid dreams or nightmares and mild or transient illusions.

While the diagnostic criteria for Parkinson’s disease-associated psychosis have changed over time, current diagnostic guidelines require that:

• clinical criteria for Parkinson’s disease diagnosis are met
• the patient is experiencing at least one of the following: illusions, false sense of presence, hallucinations, or delusions
• signs of psychosis emerge after Parkinson’s disease diagnosis
• symptoms are recurrent or continuous for at least one month
• other causes, such as other psychiatric disorders or delirium, have been ruled out.

At the clinic, doctors will want to determine not only if a person has psychosis but why it is happening. To establish the diagnosis, a clinician may:

• take a medical history, including a review of medications and diagnoses
• perform a thorough physical exam
• run lab tests to rule out other conditions that could affect cognitive state
• order brain imaging to look for structural changes that may drive psychosis
• run a battery of cognitive tests.

Data show that up to 50% of people don’t proactively discuss their symptoms of psychosis with a physician.

While it may feel frightening or embarrassing to have these symptoms of psychosis, it is important to understand it is a common symptom. Being open with your doctor about your experiences will enable healthcare professionals to provide the best possible treatment.

Treatment

Managing any symptoms of psychosis is a key aspect of Parkinson’s care. Parkinson’s psychosis treatment may involve a well-managed combination of standard Parkinson’s medications, antipsychotic treatments, and counseling or therapy.

A doctor will first perform an evaluation to make sure the psychosis or delirium is not related to other illnesses, nutritional deficiencies, or medical issues. In those situations, the underlying factors will be treated.

If the psychosis is found to be due to Parkinson’s, treatment may involve the following:

• The dose of certain Parkinson’s medications may need to be adjusted if psychosis is a side effect of those medications. Doctors will work carefully to balance the need for these medications in managing motor symptoms with keeping psychosis under control.
• Antipsychotic medications may be needed to help manage severe psychosis by balancing brain chemicals. Several classic antipsychotics, typically used for schizophrenia, aren’t recommended as they block dopamine signaling in the brain and worsen motor symptoms. Some atypical antipsychotics with different mechanisms of action may be safe and effective for people with Parkinson’s.
• There is no established therapy regimen for managing Parkinson’s psychosis, but cognitive behavioral therapy might help people cope with their psychosis symptoms, avoid depression, and manage other aspects of Parkinson’s disease.

The life expectancy of those with Parkinson’s psychosis can be enhanced through prompt and appropriate management of the condition. Although individuals with Parkinson’s psychosis may face a lower life expectancy than those without psychosis, proactive and effective care can help minimize potential risks, ultimately promoting better health and well-being for patients over a more extended period.

The impact of Parkinson’s psychosis on daily living

In its early stages, psychosis may be mild and not have substantial effects on daily life. But as it becomes more severe, living with Parkinson’s psychosis can become more disruptive and distressing, leading to many daily life challenges, which can take a substantial toll on a person’s quality of life and mental health.

Psychosis can have an impact on daily life in many ways.

• It may be very scary or upsetting to realize one is experiencing symptoms of psychosis, and it may be difficult to understand what’s happening, which can lead to anxiety or depression.
• As psychosis progresses, people with Parkinson’s psychosis may need additional support or to make changes around the house for safety. There is also an increased risk of falls and fractures. Eventually, going to an assisted living facility may be required. This can make those with Parkinson’s feel they are losing their independence.
• It’s easy to feel alone when experiencing psychosis. It can affect relationships with friends and family and make a person feel isolated or alone.

Effect on caregivers

Parkinson’s disease itself can impose substantial demands for caregivers, but dealing with both Parkinson’s disease and psychosis can be even more challenging and upsetting.

Caregivers may find it particularly difficult to provide the needed care for their loved ones, especially when those with psychosis start to lose insight, have significant behavior outbursts, or refuse to take medications.

Caregivers will have to learn new ways to interact with their loved ones and make adaptations at home to make life easier. At some point, families may have to consider outside care or a nursing home, which can be a difficult and emotional decision to make.

Like their loved ones with Parkinson’s psychosis, caregivers are at an increased risk of depression, anxiety, chronic illness, and social isolation. It’s important caregivers also seek out support systems to help avoid burnout and stay healthy.

Long-term management

Long-term management of Parkinson’s psychosis might be required in some cases. People may ask, “Can Parkinson’s psychosis be reversed?” The answer is that it depends on its cause and severity.

In some cases, making adjustments to Parkinson’s medications or treatment of other underlying factors can stop Parkinson’s psychosis entirely. But for others, psychosis may persist or get worse as the disease progresses, requiring careful long-term management to make living with Parkinson’s disease more manageable.

Some ways to help minimize the long-term impact of psychosis include:

• having routine check-ins with healthcare providers to monitor symptoms and update the treatment plan, if needed
• managing and adhering to Parkinson’s psychosis medications as prescribed by doctors, and avoiding taking any over-the-counter medications that can make psychosis worse
• finding support, which may involve getting counseling, looking into Parkinson’s support groups, or seeking out family and friends.

Parkinson’s News Today offers information and resources on living with Parkinson’s, including community support through its forums and social media platforms, Facebook and Instagram.

Caregivers can help manage psychosis over time by staying in touch with how their loved one is feeling and educating themselves about the best ways to handle it. Because Parkinson’s psychosis can be challenging for caregivers, their own self-care is another way to ensure their loved one’s well-being.

Acknowledging the potential difficulties, various initiatives are being undertaken to raise awareness about Parkinson’s psychosis. By promoting a better understanding of this condition, these efforts aim to empower affected individuals and their families to recognize the symptoms and openly discuss them with healthcare professionals, friends, and family.

Parkinson’s News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.