A person's genetic make up can directly influence the chances for the onset and development of Parkinson’s. A person's genes are inherited from their biological parents and passed along family lines to their biological children.

Current research indicates that people with a family history of Parkinson’s are more likely to develop Parkinson’s themselves. However, it is rare for multiple people in one family group to suffer from Parkinson’s.

For example, if you have two or more close relatives (parent, child, or sibling, etc) with Parkinson's, then your risk of also developing the disease increases two or three-fold, although, even at this elevated level of risk, the overall risk of developing the disease during your life is still less than 5 percent.

So, there does seem to be a genetic link for Parkinson’s Disease, but this link seems to be minor in most cases.

In order to learn more about the Parkinson’s, research has concentrated on rare family groups where multiple people have developed Parkinson's, and this research has provided useful insights into the cause of the disease in general.

Researchers have identified two types of genetic causes in families with Parkinson's Disease:

 High Levels of Specific Proteins

Abnormally high levels of alpha-synuclein, a unique protein that accumulates in degenerating brain neurons of those with Parkinson's. Other known genes include DJ-1, PINK-1, and UCHL-1, but altogether these represent far less than 1% of Parkinson's cases.

 Problems with Disposing of Unwanted Proteins

Problems with the systems in the body that dispose of unwanted proteins. The most important is a gene called parkin, which creates a protein, also called parkin. This protein helps to break down defective proteins inside brain cells (neurons). When the parkin gene is altered, or mutated, this function is impaired, and this may lead to the accumulation of defective proteins that contribute to the death of neurons. Two mutated copies of the parkin gene are needed to develop Parkinson's. This type of inheritance pattern is called autosomal recessive. One copy of the defective gene is inherited from each parent. Parkin mutations are believed to cause young-onset PD, with symptoms beginning usually in the 40s – see section Young-Onset Parkinson's. Parkin mutations are the most common genetic cause of Parkinson's, but they still account for less than 1% of all Parkinson's cases.

It is believed that both of these factors play a key role in the development of Parkinson's in all people, but further research is required.

Researchers have also found a variation in the CYP2D6 gene that appears to make people more likely to develop Parkinson's if they are exposed to certain pesticides. (See the section on 'Environmental Factors'.)