What Causes Parkinson’s Disease? Genetics, Environment, and Age Explained

When Parkinson’s disease is diagnosed in someone you love, “Why did this happen?” is often one of the questions. For most people, there is no single identified cause for Parkinson’s disease. Research points to a mix of genetic susceptibility, environmental exposures and ageing that may interact over many years. A risk factor can raise the chance of developing Parkinson’s disease without determining what happens to a person. This article explains what changes occur in the brain, what researchers know about family history and exposure, how age and sex relate to risk, and why cause, risk factor, and trigger are not interchangeable terms. It also addresses misconceptions clearly.

What happens in the brain in Parkinson’s disease

Parkinson’s disease is characterised by the progressive loss of nerve cells that produce dopamine in a part of the brain called the substantia nigra. Dopamine is a chemical messenger that helps regulate smooth movement. The substantia nigra is a brain region that contains many of these cells.

Another feature is a protein called alpha-synuclein, which is normally found in nerve cells. In Parkinson’s disease, alpha-synuclein becomes abnormal and clumps into Lewy bodies. Researchers recognise these changes as signs of the disease. How exactly these clumps relate to the loss of nerve cells is still being studied.

By the time motor symptoms become apparent, substantial loss of dopamine-producing nerve cells and dopamine in related brain pathways has already occurred. Estimates vary, and studies commonly describe around 50-60% loss of substantia nigra neurons and around 70-80% loss of striatal dopamine at symptom onset. This helps explain why changes can develop before movement problems are obvious.

Is there a single cause for Parkinson’s disease?

No, not for most people. Parkinson’s disease is thought to develop from several influences working together over many years, including genetic susceptibility, environmental exposure and ageing. Doctors use the word idiopathic — the medical term for Parkinson’s with no identifiable cause — and it describes the majority of cases. That does not mean we do not understand what happens. Instead, different factors may contribute to changes in the brain over time, with no single cause identified in most individuals. A smaller proportion of cases have a genetic cause, while many others may reflect a complex combination of genetic, environmental, and age-related influences.

Genetic factors: when Parkinson’s runs in the family

A family history of Parkinson’s disease can understandably raise worries. “Could I develop Parkinson’s disease? Could my children develop it?” I feel concerned. The reassuring point is that most people with a family history never develop Parkinson’s disease. Having a relative with Parkinson’s disease modestly raises risk. It does not mean Parkinson’s disease will be passed down.

A few rare inherited changes can directly cause Parkinson’s. Changes in PRKN (also called parkin), which helps keep proteins and mitochondria healthy, and in PINK1, which protects cells from mitochondrial damage, are usually linked with onset at a younger age. SNCA, the gene carrying the instructions for making alpha-synuclein, is another rare cause. Changes in LRRK2, a gene involved in cell signalling, and in GBA1, which helps cells clear waste, work differently: they are more common, many people who carry them never develop Parkinson’s, and GBA1-associated Parkinson’s disease tends to have a somewhat earlier onset and is associated with a higher risk of cognitive decline.

Common genetic variants may increase a person’s susceptibility without indicating whether they will develop Parkinson’s. Genetic testing can detect certain inherited changes, but it usually can’t predict the future. A neurologist or genetic counsellor can explain to you and your family what the testing and the results might mean.

Environmental and occupational exposures

Researchers have studied several environmental and workplace exposures in relation to Parkinson’s disease, including pesticides and herbicides such as paraquat and rotenone, industrial solvents such as trichloroethylene (TCE), and heavy metals such as manganese. Rural living and well-water exposure have also been investigated.

These studies show associations, not causal relationships. A 2025 review found links between Parkinson’s disease and both pesticides and TCE, although it pointed out that it can be difficult to prove causation when exposure takes place decades before diagnosis.

A 2025 nationwide Indian multicentre study found associations between Parkinson’s disease and pesticide, insecticide and fungicide exposure and head injury, while agricultural occupation itself was not significant after adjustment.

Age, sex and factors you cannot change

Age is the biggest known risk factor for Parkinson’s disease. Risk increases with age, with incidence rising after 60 and reaching its highest levels in the 70s and 80s. Young-onset Parkinson’s disease refers to diagnoses before age 50.

Parkinson’s disease is found to be more common among men than women. A 2026 FENS News report states that Parkinson’s is 1.5 to 2 times more common in men, although the reasons for this difference are not fully understood.

Age and sex can influence a person’s risk. These things do not decide if someone will get Parkinson’s. They are factors that a person cannot change, not causes that explain why Parkinson’s happens in any person.

Cause, risk factor or trigger — what the difference means

A cause produces a condition. A risk factor increases the likelihood of developing it. A trigger is a proposed event that may bring an underlying process to the point where symptoms become noticeable.

This distinction is useful when looking at health headlines and social media posts you see on the Internet. For example, a study that indicates that something “causes Parkinson’s” may actually mean that those individuals exposed to it were more likely to develop the condition. Association is not proof of causation, and especially because changes related to disease may begin years before symptoms appear.

What does not cause Parkinson’s disease

Parkinson’s disease cannot be passed from one person to another, and stress is not proven to cause it. Old age can increase the chances of developing it, although being old does not necessarily mean having Parkinson’s disease. Studies have not identified phones and vaccines as causes.

Importantly, no one should blame themselves; there is no way to know what led to Parkinson’s disease in any one person. A missed symptom, stressful period or delayed appointment should not become a source of guilt. 

How Plexus supports people living with Parkinson’s

For most people, knowing exactly why Parkinson’s disease developed does not change what comes next. What matters is understanding how the condition affects the person and building support around the activities, abilities, and goals that matter to them.

At Plexus, support begins with a doctor-led assessment of how the condition is affecting the person: tremors, movement, balance, speech, thinking and mood. A plan may then bring together physiotherapy, occupational therapy, specialised speech and movement therapy, cognitive rehabilitation, mental health therapy, and Cell Therapy for patients found eligible after assessment. Caregivers are taught the home exercises and handling techniques as part of the programme. 

The plan is reviewed regularly and adjusted as needs change. Individual outcomes vary. If you are weighing up rehabilitation support, talking through your concerns and goals with the team is a good place to start.

Frequently asked questions

What’s the cause of Parkinson’s disease?

No single cause has been identified for most cases of Parkinson’s disease. Researchers believe genetic susceptibility, environmental exposures and ageing can interact over years. These factors may increase risk without determining whether a person will develop Parkinson’s disease.

How is Parkinson’s disease caused?

Parkinson’s disease is characterised by the loss of dopamine-producing cells in the substantia nigra and changes involving alpha-synuclein, including its build-up in brain cells. This describes the disease mechanism, which is different from explaining why these changes begin in a particular person.

Why do we get Parkinson’s disease as we age?

Age is the biggest known risk factor for Parkinson’s disease, but ageing alone does not cause it. Researchers believe that ageing may interact with genetic and environmental factors over time, but they do not yet fully understand why some older people develop Parkinson’s disease while others do not. 

Is Parkinson’s disease hereditary?

A small proportion of Parkinson’s disease cases are directly linked to inherited changes, while most are not. Having a family history can modestly increase risk without meaning the condition will be inherited. A neurologist or genetic counsellor can explain whether genetic testing may be relevant.

Can pesticide exposure cause Parkinson’s disease?

Research has linked pesticide exposure with an increased risk of Parkinson’s disease, but exposure does not mean someone will develop the condition. Evidence varies between substances, so an association should not be presented as proof that pesticide exposure caused Parkinson’s disease.

Can Parkinson’s disease be prevented?

There is no proven way to prevent Parkinson’s disease. Reducing exposure to substances associated with increased risk is reasonable, particularly in occupational settings. Looking after brain and cardiovascular health is worthwhile, but these measures cannot guarantee that Parkinson’s disease will be prevented.

Sources

1. Das, S., & Ramteke, H. (2024). A comprehensive review of the role of biomarkers in early diagnosis of Parkinson’s disease. Cureus, 16(2), e54337. https://doi.org/10.7759/cureus.54337
2. Kishore, A., Borgohain, R., Puthenveedu, D. K., Rajan, R., Pal, P. K., et al. (2025). Demographic and clinical profiles of Parkinson’s disease in India: Observations from a nation-wide multicenter study. Movement Disorders, 40(10), 2220–2233. https://doi.org/10.1002/mds.30310
3. Federation of European Neuroscience Societies. (2026, July 8). Why does Parkinson’s disease affect more men than women? Study reveals differences in gene activity in the brain. FENS News. https://www.fens.org/news-activities/news/why-does-parkinsons-disease-affect-more-men-than-women-study-reveals-differences-in-gene-activity-in-the-brain
4. Atterling Brolin, K., Schaeffer, E., Kuri, A., Rumrich, I. K., Schumacher Schuh, A. F., Darweesh, S. K. L., Kaasinen, V., Tolppanen, A.-M., Chahine, L. M., & Noyce, A. J. (2025). Environmental Risk Factors for Parkinson’s Disease: A Critical Review and Policy Implications. Movement Disorders, 40(2), 204–221. https://pmc.ncbi.nlm.nih.gov/articles/PMC11832802/ 

Educational disclaimer: For educational purposes only, not medical advice. Treatment decisions require professional consultation.

Medically Reviewed By

Dr. Na’eem Sadiq

Medical Director of Plexus

Medically reviewed: September 28, 2026

Dr. Na’eem Sadiq is a neurologist and neuropsychiatrist with over 35 years of clinical experience in treating complex neurological disorders. He founded Plexus in 2011 with a mission to enhance the quality of life for people living with neurological conditions. His areas of expertise include Neurology, Parkinson’s Disease, Multiple Sclerosis, Epilepsy, Migraine, Demyelinating Polyneuropathy and Cell Therapy.