Parkinson’s disease is probably best known for causing motor symptoms like tremors and stiffness. But many people with this condition also have mental health symptoms, including depression and anxiety.

Psychosis is a more severe symptom in which people lose touch with reality. Between 20 and 40 percent of people with Parkinson’s disease have symptoms of psychosis in the early stages of the disease. By the late stages, up to 70 percent of people will experience psychosis.

Parkinson’s psychosis can be challenging to manage, but medications can help to relieve these symptoms.

The two main symptoms of Parkinson’s psychosis are:

  • Hallucinations: seeing, hearing, smelling, tasting, or feeling things that aren’t real.
  • Delusions: believing things that aren’t true.

Hallucinations can affect any of the five senses:

  • Sight (visual). Seeing something that isn’t there, such as insects crawling on the walls or a deceased relative.
  • Hearing (auditory). Hearing voices or sounds that aren’t real.
  • Smell (olfactory). Smelling an odor that isn’t there, like cookies baking or a skunk’s spray.
  • Feeling (tactile). Feeling imaginary things, like bugs crawling on your skin.
  • Taste (gustatory). Having a strange taste in your mouth that isn’t from something you’ve eaten or a medical condition.

Some people sense the presence of a person or an animal nearby. Others see real objects transform into other things — for example, a vase changes into a dog.

It’s more common to have hallucinations at night, when the darkness creates shadows. Hallucinations can last anywhere from a few seconds to a few minutes.

Early in the disease, most people with Parkinson’s psychosis have insight, which means they understand that what they’re experiencing isn’t real. Later in the disease, often people lose insight and believe that what they see, hear, or feel is real.

Delusions are thoughts that aren’t grounded in reality. They’re not as common as hallucinations, affecting only about 8 percent of people with Parkinson’s disease. But they are harder to treat.

The most common delusions involve paranoia — for example, the feeling that people are out to get you, or that your partner is cheating on you. Having these thoughts can lead to aggressive or even dangerous behavior.

You’ll start with a visit to your doctor for an evaluation. Your doctor may diagnose you with this condition if you:

  • have had symptoms like hallucinations and delusions for at least 1 month
  • don’t have another condition that could be causing these symptoms, like dementia, delirium, major depression, or schizophrenia

Not everyone with Parkinson’s disease will develop psychosis. You’re more likely to have this if you:

  • are older
  • have lived with Parkinson’s for a while
  • have dementia or delirium
  • are depressed
  • take Parkinson’s medication, or recently changed your dose
  • have a sleep disorder such as insomnia or sleep apnea
  • have vision or hearing problems

There are two possible causes of Parkinson’s psychosis:

  • changes in levels of brain chemicals like serotonin and dopamine from the disease itself
  • changes in levels of these chemicals from medications that treat Parkinson’s disease

Dopamine is a chemical that helps your body move smoothly. People with Parkinson’s disease have lower than normal levels of dopamine, which causes their body to move stiffly.

Drugs that treat Parkinson’s improve movement by increasing dopamine levels. Yet they can sometimes cause psychosis as a side effect.

Because Parkinson’s drugs can cause psychosis, your doctor will likely start by taking you off your medications, one at a time, or adjusting the dose. Changing your medication may make your movement symptoms worse.

Your doctor will keep adjusting your medication. The goal is to get you to a dose that improves your movement without causing hallucinations and delusions.

If changing your medication doesn’t work, the next step is to go on an antipsychotic medication. These drugs prevent psychosis symptoms by altering levels of chemicals in your brain.

Older antipsychotic drugs can make Parkinson’s movement symptoms worse. Newer drugs, called atypical antipsychotics, are less likely to affect your movement. These drugs are off-label, meaning they’re not approved to treat Parkinson’s specifically. They include:

  • clozapine (Clozaril)
  • quetiapine (Seroquel)

In 2016, the Food and Drug Administration approved pimavanserin (Nuplazid). It’s the first drug designed specifically to treat Parkinson’s disease psychosis. Nuplazid reduces the number of hallucinations and delusions without affecting movement.

Nuplazid and other newer antipsychotic drugs do carry a black box warning. They can increase the risk of death in older people who have psychosis related to dementia. Your doctor will consider this and other risks before prescribing one of these drugs.

Caring for someone who sees, hears, or believes things that aren’t real can be very difficult. Try to be as patient and calm as you can.

Avoid arguing with the person. If they still have insight, gently explain that what they’re seeing isn’t real. Tell anyone who cares for or visits your loved one what to expect, and how to respond.

Stay in close contact with the person’s doctor. If their symptoms don’t improve, ask whether they need a medication adjustment.

Check whether the person needs hearing aids or glasses. Poor hearing or vision can sometimes lead to hallucinations. It can also help to turn on bright lights at night, to prevent the shadows that may trigger visual illusions.

Secure any dangerous objects, and keep pathways in the home clear to prevent falls and injuries. If you ever feel like the person is a risk to themselves or others, call their doctor.

Parkinson’s psychosis can be one of the most challenging aspects of caring for someone with this disease. Try to be patient with the person, and get help from their doctor or a mental health professional when you need it.

Adjusting the dose of Parkinson’s medications is one way to relieve psychosis symptoms. If that doesn’t work, taking an antipsychotic drug may help.