We do not know exactly what causes Parkinson's disease (PD), but scientists believe that a combination of genetic and environmental factors are the cause. The extent to which each factor is involved varies from person to person. Researchers do not know why some people develop Parkinson's and others do not.
Genetics cause about 10% to 15% of all Parkinson's. In some families, changes (or mutations) in certain genes are inherited or passed down from generation to generation. A handful of ethnic groups, like the Ashkenazi Jews and North African Arab Berbers, more commonly carry genes linked to PD and researchers are still trying to understand why.
Regardless of how a person gets Parkinson's — through genetics or environment or a combination of both — every person with PD experiences a loss of dopamine in the brain, along with symptoms and a progression of their disease that is unique to them.
Understanding the connection between Parkinson's and genetics can help us understand how the disease develops and ultimately how it can be treated or cured. This is why studies like the Parkinson's Foundation Genetics Initiative that is linking genetics to Parkinson's are essential.
Over the years, scientists have studied DNA from people with Parkinson's, comparing their genes. They discovered dozens of gene mutations linked to Parkinson's. These genes are now being researched and studied for what role they play in Parkinson's.
Even when someone has a gene mutation associated with Parkinson's, the likelihood of developing the disease is low. This is because researchers are only beginning to understand the role genes play in Parkinson's — like if certain genes cause Parkinson's and how other genes may protect some people from developing it.
Right now, we know that inherited genetics, environmental influences and lifestyle choices collectively determine if someone will develop Parkinson's.
What If I Carry the Gene?
Parkinson's is rarely hereditary (passed from generation to generation). If a person tests positive for a certain gene mutation associated with Parkinson's — such as a mutation in LRRK2 or GBA genes — their risk may increase, but they may still never develop Parkinson's.
It is possible for someone who tests positive for a Parkinson's mutation to inherit other genes, be exposed to environmental factors or have lifestyle choices that do not lead to developing Parkinson's.
There are ongoing clinical trials testing therapies to treat people who have Parkinson's and carry certain gene mutations. Proving that it can be important to know which gene mutation you carry. Consult with your doctor when considering a genetic test to determine if you are eligible to participate in gene-based clinical trials. One study, the Genetics Initiative, is the first national Parkinson's study to offer free genetic testing plus counseling for Parkinson's-related genes through medical professionals.