What Causes Parkinson's Disease?

Scientists are finding answers to this question: How do you get Parkinson’s disease? What causes Parkinson’s disease involves genetic and environmental factors.

Researchers now understand Parkinson’s disease results from the loss of brain cells that produce dopamine, a chemical the body needs to send signals within the brain that are crucial for normal body movements. But scientists are still trying to figure out why the dopamine-producing brain cells are affected in the first place.

Although exactly what causes Parkinson's disease (PD) remains unknown, research has accumulated that indicates how you get Parkinson’s disease depends on a combination of both environmental and genetic factors.

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How do you get Parkinson’s disease?

Some factors that increase the risk for developing PD have been identified — including male gender, advancing age (being 60 years old or older), and experiencing a head trauma resulting in a change in consciousness.

Over the past 10 years, scientists have identified rare genetic mutations that may cause some cases of Parkinson’s disease. They’ve also found other genetic changes that may interact with environmental chemical exposures to trigger PD. Some people may have a genetic makeup that makes them either more or less likely to be affected by toxic substances that might cause PD.

Bottom line: There appears to be a continuum of causes of Parkinson’s disease, and they effect individuals differently, according to PD experts at the Michael J Fox Foundation for Parkinson’s Research.

Imagine a chart with genetic factors on one end and environmental factors at the other. All Parkinson’s disease patients would likely fall somewhere on the chart but at different spots, depending on their own specific genetic make-up and exposures to pesticides and other chemicals.

Causes of Parkinson’s disease

In the early 1980s, a dramatic example of how a specific chemical exposure could be one of the causes of Parkinson’s disease was discovered when several heroin users in California used drugs contaminated with a substance called MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) – and they developed Parkinson's disease. As a result of this tragedy, scientists were able to study how MPTP destroys dopamine-producing brain cells and use this knowledge to further research into how certain chemical exposures might be causes of Parkinson’s disease.

The Parkinson’s Foundation lists these environmental exposures as potential causes of Parkinson’s disease:

• Exposure to pesticides (including permethrin and beta-hexachlorocyclohexane) over a long period of time, especially as part of a person’s profession, has been consistently linked to higher rates of Parkinson’s disease.
• A study by Northwestern Medicine scientists, published in Nature Chemical Biology, has identified genes that may lead to Parkinson's disease after exposure to paraquat, an herbicide used on a restricted basis in the U.S. but widely used in Asia. In addition, the herbicide 2,4-dichlorophenoxyacetic acid may also be linked to PD. This chemical was used in the defoliant Agent Orange during the Vietnam War era. Although it has not been officially designated as one of the causes of Parkinson’s disease, research has suggested a link a between the development of PD and exposure to Agent Orange and the fungicide maneb – and the U.S. Department of Veterans Affairs has ruled veterans with Parkinson’s disease who served in Vietnam and were likely exposed to these chemicals are eligible to receive disability compensation from the VA.
• Occupational exposures to various metals have been associated with the development of Parkinson’s disease in some studies, but not in others, so the potential PD risk is unknown at this time.
• Trichloroethylene (TCE) and polychlorinated biphenyls (PCBs)are chemicals used in many industries and the most common organic contaminants in groundwater. Occupational exposure to TCE has been linked to a higher risk of Parkinson’s disease among workers whose jobs exposed them to his solvent from eight to 33 years. PCBs have been found in relatively high concentrations in the brains of people who suffered from Parkinson’s disease, and occupational exposure to PCBs is associated with a greater risk of Parkinson’s in women, but not in men.

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