Disorders

What is Parkinson's disease?

Reviewed June 2026 by Allan D. Wu, MD, FAAN

Definition: Parkinson’s disease is a progressive brain disorder. It primarily affects movement, but it can also affect many other aspects of a person’s health and daily life. The main movement symptoms occur when nerve cells in the brain that make dopamine, a chemical that helps control movement, begin to break down.

Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's disease, and experts consider it the fastest growing neurodegenerative condition in the world.

While most people are diagnosed after age 60, about 5–10% develop symptoms before age 50. Symptoms usually emerge gradually, sometimes making early diagnosis difficult. There are many treatment and management options for Parkinson's disease, and more research is being done all the time.

If you or someone you love is noticing symptoms, you are not alone. Treatment, rehabilitation, and support can help many people manage symptoms and maintain quality of life.

What are the symptoms of Parkinson’s disease?

Parkinson's disease symptoms usually appear slowly over time, and they vary from person to person. The symptoms fall into two categories: movement-related symptoms and other non-movement symptoms.

Movement symptoms can include:

  • Tremor (shaking), often at rest and typically starting on one side of the body
  • Stiffness in the arms, legs, or torso
  • Slower movement or difficulty starting to move
  • Changes in balance or coordination
  • Softer voice or reduced facial expression
  • Smaller handwriting

Other symptoms can include:

  • Loss of sense of smell
  • Sleep problems
  • Mood changes
  • Fatigue
  • Constipation
  • Difficulty with memory and focus

These symptoms can have a real impact on daily life, and many can be treated. Recognizing them early can help you and your neurology care team plan next steps  

What are the causes and risk factors of Parkinson’s disease?

The exact cause of Parkinson’s disease is still being studied. What researchers do know is that a protein called alpha-synuclein builds up abnormally in nerve cells that release dopamine, damaging them gradually over time. This is why Parkinson's disease affects not just movement but also can affect sleep, mood, digestion, and thinking.

Researchers believe this happens because of a combination of biological, genetic, and environmental risk factors. For most people, Parkinson’s disease is not caused by any one factor. Instead, it likely develops from a mix of factors over time.

It’s important to remember that having a risk factor doesn’t mean you’ll develop Parkinson’s disease.

Some risk factors include:

  • Age: Risk increases as people get older.
  • Sex: Parkinson’s is more common in men than women.
  • Genetics: Some people carry gene changes that increase risk.
  • Environmental exposures: Long-term exposure to certain chemicals, including some pesticides or industrial solvents, has been associated with increased risk.

How is Parkinson’s disease diagnosed?

Parkinson’s disease is always diagnosed clinically by doctors. That means doctors make this diagnosis based on your medical history, medication history, symptoms, and neurological exam. 

No single laboratory test or scan can confirm Parkinson’s disease on its own. A strong improvement in symptoms after starting levodopa, a common and effective drug for Parkinson’s disease, can also support a diagnosis. 

For many patients, a confident diagnosis can be made with these observations without additional testing.

However, diagnosing Parkinson’s disease isn’t always straightforward, and it can share symptoms with other conditions. This is when additional tests can help confirm the diagnosis or point toward a different condition:

  • Imaging: Standard brain imaging (MRI scans) can help rule out other issues like stroke or tumors. These scans are usually normal in people with Parkinson’s disease.
  • Dopamine transporter scan (DaTscan): Since Parkinson’s disease affects the dopamine system, this nuclear imaging scan uses a small amount of radioactive tracer to look at dopamine activity in the brain. However, it doesn’t distinguish between Parkinson’s disease and some similar conditions.
  • Seed amplification assays (SAA): This newer test looks for abnormal alpha-synuclein protein in spinal fluid. Studies suggest this may be a biomarker for Parkinson’s disease, meaning that it can support a diagnosis and also follow disease progression.
  • Skin biopsy (Syn-One test): This test uses a small skin sample to look for abnormal alpha-synuclein protein in nerve fibers. It can help support a diagnosis of Parkinson’s disease, but it doesn’t rule out some other conditions.

No combination of tests can make a diagnosis of Parkinson’s disease 100% certain, and even a positive test doesn’t automatically mean you have the condition. An experienced doctor should always confirm the diagnosis.

Follow-up visits with your doctor are important because Parkinson’s symptoms can change over time. Regular monitoring helps your care team adjust your diagnosis and treatment plan as needed.

What treatments are available for Parkinson's disease?

There’s no cure for Parkinson’s disease, but many treatments can help manage symptoms, support independence, and improve quality of life.

  • Medications: The most common and effective medicine is levodopa, often combined with carbidopa. It helps replace dopamine in the brain and can improve movement symptoms. Other medicines may also help support dopamine levels. Over time, some people develop periods when medication wears off or involuntary movements called dyskinesias, which may require treatment changes. Newer formulations of these medications can make these problems less likely.
  • Deep brain stimulation (DBS): For some people whose symptoms are not well controlled with medication alone, deep brain stimulation may be an option. In this procedure, electrodes are placed in specific areas of the brain and connected to a small device under the skin. The device sends electrical signals that can help reduce tremor, motor fluctuations, and dyskinesias. These signals can be adjusted for better symptom control.
  • Focused ultrasound (FUS): Focused ultrasound uses sound waves guided by MRI to destroy a small area of brain tissue that contributes to Parkinson's movement symptoms. It may be an option for people who can’t or don’t want to have DBS. Unlike with DBS, however, effects are permanent and can’t be reversed or adjusted.
  • Therapies and exercise: Physical therapy, occupational therapy, and speech therapy are important parts of Parkinson’s care. Regular exercise, especially aerobic activity and balance training, can improve mobility, mood, and overall quality of life.

Parkinson's care often extends beyond this list. Many symptoms, such as depression, anxiety, sleep problems, and others, can be managed specifically. Your care team, which may include a neurologist, primary care doctor, and other specialists or therapists, can help address them. Don't hesitate to bring your symptoms up at each visit.

Caring for and navigating Parkinson's disease

Explore practical tips, personal stories, and expert guidance for living well with Parkinson’s disease.

Frequently asked questions

Is Parkinson’s disease hereditary?

For most people, Parkinson’s disease is not directly inherited.

Still, genetics can play a role. Some people carry gene changes that increase risk, and having a close family member with Parkinson’s disease may slightly raise your chances. Even so, most people with a family history will never develop Parkinson’s disease.

Researchers believe Parkinson’s disease usually develops from a combination of biological, genetic, and environmental factors, not just one cause.

What are the stages of Parkinson’s disease?

Parkinson’s disease is sometimes described in five stages based on the severity of movement symptoms:

  • Stage 1: Symptoms affect only one side of the body. There is minimal impact on daily activities. Changes may be so mild they go unnoticed.
  • Stage 2: Symptoms spread to both sides of the body. Daily tasks may take longer, but the person remains independent. Posture and walking may be affected.
  • Stage 3: Considered mid-stage. Balance problems become more noticeable and falls are more common. The person is still physically independent, but daily activities are significantly affected.
  • Stage 4: Symptoms are severe. Walking may still be possible but is limited. The person needs help with daily activities and cannot live alone safely.
  • Stage 5: The most advanced stage. The person may be unable to stand or walk without assistance and may require a wheelchair or be bedridden. Around-the-clock care is typically needed.

It is important to know that this staging system focuses only on movement symptoms and does not capture the full experience of Parkinson's disease. People don’t move predictably from one stage to the next—progression varies widely, and many people live for years without significant advancement.

Neurologists prefer to track a much broader range of movement symptoms, non-movement symptoms, and medication needs to understand where a given patient and family is on the Parkinson’s disease journey.

What research is being done, and how can I participate in clinical trials?

Research on Parkinson’s disease is active and ongoing.

Some key areas of research include:

  • Disease-modifying therapies: Drugs targeting the underlying biology of Parkinson’s disease.
  • Biomarkers for early detection: Tests that may allow earlier, more precise diagnosis. 
  • Cell replacement therapy: Transplanting dopamine-producing cells derived from stem cells into the brain.
  • Advanced brain stimulation: Newer "adaptive" deep brain stimulation systems that respond in real time to brain signals.
  • Lifestyle research: Studies examining whether exercise, diet, and other lifestyle factors can protect the brain and slow disease progression.
  • Symptom-focused research: Studies targeting specific Parkinson's symptoms, including movement problems, depression, memory changes, sleep problems, and low blood pressure, are ongoing and may be open to people at various stages of the disease.

If you’re interested in taking part in research, these resources may help. Ways to find out more on your own include:

  • Fox InsightAn online study where people with Parkinson’s disease and their loved ones complete surveys about symptoms, daily life, and health experiences. No clinic visits are required.
  • PD GENEration studyAn international research initiative offering no-cost genetic testing and counseling for people living with Parkinson’s disease, sponsored by the Parkinson's Foundation.
  • The Parkinson's Precision Medicine Initiative (PPMI)A landmark longitudinal study, sponsored by The Michael J. Fox Foundation, open to people with Parkinson's disease, family members, and people who don’t have the disease. Most participants begin online and complete remote tasks like a scratch-and-sniff smell test. Some may be invited to participate further at a clinical site.

You can also discuss joining a clinical trial with your doctor or care team. These tools help match you with studies that may require eligibility screening, in-person visits, or medical history review:

What should caregivers know about supporting someone with Parkinson’s disease?

Parkinson’s disease is progressive, which means care needs can change over time. Caring for someone with Parkinson’s can place physical, emotional, and financial demands on caregivers, so support matters for you, too.

Here are a few important things caregivers should know:

  • Medication timing matters: Many Parkinson’s disease medicines work best when they’re taken on a regular schedule. Helping your loved one stay on track can make a meaningful difference.
  • Watch for non-movement symptoms: Depression, anxiety, sleep problems, and thinking changes are common in Parkinson’s disease and can be just as challenging as movement symptoms. Share these concerns with your neurology care team.
  • Home safety: As balance and mobility change, home adjustments such as removing tripping hazards, adding grab bars, and improving lighting can help reduce the risk of falls.
  • Take care of yourself: Caregiver burnout is real. Support groups, respite care, counseling, and help from family or friends can all make caregiving more sustainable.
  • Build a care team: Neurologists, advanced practice providers, physical therapists, occupational therapists, speech therapists, and social workers can all play a role. You don’t have to manage this alone.
  • Plan ahead for hospital visits: Hospital staff may not be familiar with the unique needs of Parkinson's disease patients.