Causes of Parkinson’s What is Parkinson’s Disease? Causes of Parkinson’s Theories About What Causes Parkinson’s The cause of Parkinson’s disease (PD) is still unknown, although there is some evidence for the role of genetics, environmental factors, or a combination of both. It is also possible that there may be more than one cause of PD. Scientists generally believe that both genetics and environment interact to cause Parkinson’s disease in most people who have it. Currently, there is an enormous amount of research directed at producing more answers about what causes Parkinson’s disease and how it might be prevented or cured. When physicians diagnose PD, they often describe it as idiopathic (ID-ee-oh-PATH-ik). This simply means that the cause of Parkinson’s disease is not known. Genetic factors Scientists estimate that less than 10% of cases of Parkinson’s disease are primarily due to genetic causes. The most common genetic effect that triggers Parkinson’s disease is mutation in a gene called LRRK2. The LRRK2 defect is particularly frequent in families of North African or Jewish descent. Mutations in alpha-synuclein have also been found to trigger PD, but these are quite rare. In most cases of PD, no primary genetic cause can be found. Environmental factors Certain environmental factors, such as significant exposure to pesticides or certain heavy metals and repeated head injuries, can increase risk of PD. Most people do not have a clear environmental cause for their PD, and because many years can pass between exposure to an environmental factor and the appearance of Parkinson’s disease symptoms, the connection is often difficult to establish. However, it seems likely that environmental factors do influence the development of PD, perhaps particularly in people who also have a genetic susceptibility. Other risk factors There are other things that put an individual at higher risk for developing PD. The main risk factor is age, because Parkinson’s disease is more common in older adults (>50 years of age). Men also have a higher risk of Parkinson’s disease than women. Parkinson’s disease often seems to affect Caucasians more than African Americans or Asians. The actual links between any of these factors and Parkinson’s disease are not completely understood.