Jun 22, 2026
Written by Patricia Weiser, PharmD | Last updated April 6, 2026
Fact-checked by Patrícia Silva, PhD
If your parent is living with Parkinson’s disease, you may eventually notice changes that go beyond symptoms that affect mobility. Some patients begin to see, hear, or sense things that others do not. These experiences can be part of Parkinson’s psychosis.
These symptoms are more common than many families realize. Research suggests that 20% to 40% of people with the disease experience hallucinations or delusions. Recognizing these signs early and discussing them with your parent’s care team can help guide care decisions.
Signs to watch for in your parent
Spotting early Parkinson’s psychosis symptoms may be difficult because they are often subtle and may be mistaken for normal aging or fatigue. Your parent may also feel embarrassed or unsure about how to talk about what they are experiencing.
While symptoms can look different from person to person, Parkinson’s psychosis most often appears as hallucinations, illusions, or delusions.
Hallucinations
Hallucinations in Parkinson’s involve seeing, hearing, or sensing things that are not actually there. Hallucinations may last only seconds or minutes. You might notice your parent:
- seeing people, animals, or unfamiliar figures
- hearing voices, music, or knocking that others do not hear
- talking to relatives, neighbors, or pets that died long ago
Illusions
Illusions are similar to hallucinations but occur when something real is misinterpreted. These experiences can happen when the lighting is dim or when an object is viewed from a distance. Examples of illusions may include mistaking a shadow, a coat rack, or a lamp for a person, or believing someone moved in the room when it was only a shifting shadow.
Jun 19, 2026
Medically reviewed by Heidi Moawad, M.D. — Written by Jill Seladi-Schulman, Ph.D. on May 23, 2023
Parkinson’s disease (PD) is a progressive neurological disorder that affects movement as well as mental and emotional changes. The exact cause is unknown, but researchers are investigating if autoimmune factors may play a role.
PD is a neurological disorder where nerve cells in your brain become damaged or begin to die. While the cause of PD is unknown, there’s evidence that the immune system might be involved.
Below, we’ll cover more about PD and how autoimmune activity could contribute to it. Keep reading to learn more.
Autoimmune diseases happen when your immune system mistakenly attacks healthy tissues. This can cause inflammation and tissue damage in the affected areas of your body.
There are many different types of autoimmune diseases. Some that you may be familiar with include:
- lupus
- rheumatoid arthritis
- psoriasis
- type 1 diabetes
- multiple sclerosis
The exact cause of PD is unknown, and it’s currently not considered an autoimmune disease. While there’s some evidence that immune factors might be associated with PD, there’s no evidence so far that these immune factors actually cause PD.
A 2017 study found that PD may have genetic factors in common with some autoimmune diseases such as diabetes, ulcerative colitis, rheumatoid arthritis, and others.
Jun 15, 2026
Evidence for motor and nonmotor benefits remains limited, researchers say
Written by Lila Levinson, PhD | June 10, 2026
- Fecal microbiota transplantation (FMT) shows promise for Parkinson’s-related constipation.
- FMT was generally safe and beneficial for gastrointestinal symptoms in people with Parkinson’s.
- Evidence for broader motor and nonmotor benefits is inconsistent, and more high-quality research is needed.
Fecal microbiota transplantation (FMT), a technique for replacing gut bacteria, may help with gastrointestinal symptoms of Parkinson’s disease, particularly constipation, according to a review study.
While the technique was found to be generally safe and beneficial for gastrointestinal symptoms in Parkinson’s disease, “at this stage, there is no convincing evidence that FMT produces a clinically relevant motor or non-motor symptomatic improvement on a group basis, at least in the short to medium term,” the researchers wrote.
Evidence on FMT remains limited
The researchers noted that available studies about FMT in Parkinson’s use a variety of different techniques, and many have methodological limitations. Future high-quality research could help clarify the potential benefits of FMT in this context.
The study, “Safety and efficacy of faecal microbiota transplantation in Parkinson’s disease,” was published in npj Parkinson’s Disease.
Parkinson’s is a neurological condition that leads to a variety of motor and nonmotor symptoms. Constipation and other gastrointestinal problems are among the possible nonmotor signs of the condition.
Parkinson’s and the digestive tract have a complex relationship. Not only can Parkinson’s cause gastrointestinal symptoms, but the bacteria and other microorganisms living in the intestines, collectively known as the gut microbiota, may influence certain disease processes. For example, the review noted that animal studies suggest that gut microbiota from people with Parkinson’s may promote inflammation and nerve degeneration.
These connections have led scientists to wonder whether altering the gut microbiota could be used as a treatment strategy for Parkinson’s. One way to do this is with FMT, which the researchers described as “an ultimate treatment for replacing the host microbiota with that of a healthy donor.”
There are several methods for performing FMT. Typically, they involve first collecting gut bacteria from donors’ stool. Patients receive the transplant as a capsule, an enema (a liquid placed into the rectum), or a procedure delivering the sample directly to the digestive system.
The team aimed to comprehensively examine existing research about FMT in Parkinson’s, which remains limited. “This review examines the current evidence on FMT in [Parkinson’s disease] concerning safety, efficacy, and microbiome changes, and analyses the data in the perspective of recommendations for future studies in this field,” they wrote.
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