If you or someone you love has been diagnosed with Parkinson’s disease, you probably have questions about why it happened. And if you’re worried about developing the condition yourself, you may wonder what puts someone at risk and whether there’s anything you can do about it. The tricky part? There’s no single, clear-cut answer as to what causes Parkinson’s disease.
Researchers believe Parkinson’s develops through a combination of factors, including a person’s biology, genetic makeup, and environmental exposures. Age also plays an important role. Additionally, scientists have identified several factors that may make someone more likely to develop the disease.
Taken together, it’s possible to understand who is at risk for Parkinson’s disease, even if the exact cause is still unknown.
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What Happens in the Brain During Parkinson’s Disease
Parkinson’s disease happens when cells become weakened or damaged in a part of the brain called the substantia nigra. The cells in this area produce dopamine, a chemical messenger that sends signals between nerves to control things like movement, memory, and mood, per the National Institute of Neurological Disorders and Stroke (NINDS). “As the number of cells [in the substantia nigra] decreases, your brain has less dopamine available,” explains neurologist Daniel Truong, M.D., the medical director of the Truong Neuroscience Institute at MemorialCare Orange Coast Medical Center in Fountain Valley, CA.
The decrease in dopamine can lead to movement-related symptoms like slowness, stiffness, tremors, trouble walking, and balance issues. And because dopamine is involved in other functions, Parkinson’s symptoms can also impact a person’s sleep, digestion, thinking, and sense of smell. It can also increase their risk for anxiety and depression.
“The biological changes [in the brain] associated with Parkinson’s may begin years, and possibly even decades, before the movement symptoms that lead to diagnosis appear,” says Chris Krueger, the senior manager of educational content for the Davis Phinney Foundation for Parkinson’s in Louisville, CO, who himself lives with Parkinson’s disease. In fact, most people with Parkinson’s disease have lost between 60% and 80% of the dopamine-producing cells in their substantia nigra by the time they start having movement-related symptoms, according to NINDS.
Is Parkinson’s Disease Genetic?
Genetics plays a small role in Parkinson’s disease. Between 10% and 15% of people who develop the condition have a family history, per Johns Hopkins Medicine. In those cases, a person carries a genetic mutation linked to Parkinson’s (common mutations include changes to the LRRK2, PARK2, PARK7, PINK1, and SNCA genes).
Having one of these genetic mutations can make a person’s brain cells more vulnerable to the changes that lead to Parkinson’s. For instance, the mutations may allow more oxidative stress to build up in brain cells, which can cause the cells to become damaged, per NINDS.
Still, having a relative with Parkinson’s doesn’t guarantee that you’ll also get it. “There is increasing recognition that just like every chronic disease, the risk of getting Parkinson’s is due to both a person’s genetic makeup and their environmental exposures. It is typically not one specific thing that causes Parkinson’s disease, it is a combination of lots of things,” says Rebecca Gilbert, M.D., Ph.D., Chief Mission Officer for the American Parkinson Disease Association headquartered in New York City.
Can Environmental and Toxin Exposure Cause Parkinson’s?
Increasing evidence suggests that people with long-term exposure to certain chemicals, such as the pesticide paraquat, are more likely to develop Parkinson’s than those who aren’t exposed. Ongoing exposure to solvents like trichloroethylene (TCE), a chemical used in degreasers and in dry cleaning, and various heavy metals may also play a role, according to the Parkinson’s Foundation.
These substances may slowly cause damage to cells in the brain, notes a paper published in the Journal of Parkinson’s Disease. They “can interfere with the cells’ ability to produce energy, increase oxidative stress, and disrupt the mechanisms that normally remove damaged proteins,” Dr. Truong says.
As with family history, not everyone who is exposed to these chemicals will get Parkinson’s. “The risk depends on the type of toxin, intensity and duration of exposure, genetic susceptibility, and other factors,” Dr. Truong says. Often, the risk is higher for people who have regular or frequent exposure because of their jobs, the Parkinson’s Foundation notes.
What Are the Main Parkinson’s Disease Risk Factors?
Certain variables don’t directly cause Parkinson’s, but they can increase a person’s risk, according to NINDS and the Parkinson’s Foundation. Three of the most significant risk factors for the disease are:
- Age. Parkinson’s disease risk starts to increase in a person’s mid-60s.
- Biological sex. Parkinson’s is more common in men than in women.
- Head injury. Concussions that alter a person’s level of consciousness are tied to a higher risk of developing Parkinson’s disease later in life.
Parkinson’s Disease vs. Drug-Induced Parkinsonism
Certain medications can cause movement symptoms that look similar to Parkinson’s, but it’s not the same. This phenomenon is called drug-induced parkinsonism. Per a Neurology International paper, it’s most often caused by antipsychotic and anti-nausea medications that interfere with dopamine signaling in the brain, such as:
- Haloperidol. This antipsychotic is used to treat mental disorders such as schizophrenia and control the movements and vocal tics associated with Tourette syndrome.
- Maprotiline. This medication is used primarily to treat depression.
- Metoclopramide. This medication is used to treat nausea, vomiting, and delayed stomach emptying, as well as certain cases of persistent acid reflux.
- Risperidone. This antipsychotic is commonly used to treat bipolar disorder and irritability associated with autism.
- Sulpiride. This medication treats schizophrenia.
- Tiapride. This antipsychotic may be used to treat severe involuntary movements and short-term agitation or aggression.
Parkinson’s is a progressive neurodegenerative disorder, while drug-induced parkinsonism is a medication side effect. “If the symptoms are due to a drug and the drug is stopped, the symptoms will resolve,” Dr. Gilbert says. It may take between six and 12 months, though some people can experience longer-lasting effects, according to a paper published in the journal Cureus.
Can Parkinson’s Disease Be Prevented?
There’s no proven way to prevent Parkinson’s. But lifestyle changes may lower your risk or make it easier to manage symptoms, says the Parkinson’s Foundation.
At the top of the list: Regular exercise, which may lower a person’s chance of Parkinson’s by as much as 21%, noted a paper published in the journal Cells. “It’s among the most promising strategies,” Dr. Truong says. “Exercise improves blood flow to the brain, supports nerve-cell health, and may strengthen the brain’s ability to adapt to age-related changes.”
Other examples of Parkinson’s disease self-care that may also have protective benefits against developing the disease, per the Cells paper:
- Do activities that keep your brain engaged
- Eat a healthy diet rich in fruit, vegetables, whole grains, nuts, beans and legumes, fish, coffee, and tea
- Get enough sleep
- Get enough vitamin D
- Limit your alcohol intake and avoid smoking
- Maintain strong social ties
Common Myths About What Causes Parkinson’s
The proliferation of certain falsehoods about Parkinson’s disease, often making the rounds on social media, has made it difficult for experts to improve the public understanding of what causes the condition. These are some of the common myths that are not true.
Parkinson’s Disease Always Runs in Families
In up to 85% of cases, a specific cause can’t be identified, per Johns Hopkins Medicine. “Although genetics can affect risk, most people with Parkinson’s do not have a clearly inherited form of the disease,” Krueger says.
Parkinson’s Disease Only Affects Older White Men
Anyone can develop Parkinson’s. “These misconceptions may have caused Parkinson’s to be overlooked and contributed to delays in diagnosis and treatment for groups of people known to have a longer time between symptom onset and diagnosis, especially women, people of color, and younger people,” Krueger says.
You Caused Yourself to Get Parkinson’s
Parkinson’s disease is a complex condition, and it’s not your fault if you have it. “It is not something you caused by worrying too much, working too hard, failing to exercise, or making the wrong lifestyle choices,” Dr. Truong says.
When to Talk to a Doctor About Parkinson’s Symptoms
Early treatment and intervention can make Parkinson’s disease more manageable. Talk to your doctor as soon as possible if you suspect that you or a loved one is having possible symptoms. Per the Mayo Clinic, these include:
- Handwriting that has become smaller or cramped
- Needing to think about doing automatic movements like blinking, smiling, or swinging your arms when you walk
- Non-motor symptoms like depression, anxiety, constipation, needing to urinate more often, trouble smelling, fatigue, or acting out your dreams
- Poor posture or balance
- Shaking hands or fingers
- Slowed movement, like taking longer to get out of a chair or get dressed
- Speech changes, like speaking more softly or quickly
- Tense or stiff muscles
In all these cases, there are plenty of other non-Parkinson’s explanations for the symptom, and most people never develop Parkinson’s. But if you do have the condition, identifying it early can help you and your doctor work together on a treatment plan so you can manage your symptoms and keep living a full life.
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