The earliest memories of I have of Parkinson's Disease (PD) is watching Back to the Future, one of my favorite movies, and having it explained to me that Marty had a disease that made him twitchy. As I grew, I came to the understanding, wrongly so, that Parkinson's was a result of a loss of the myelin sheath on axons. In high school I did a mini presentation on the disease and discovered that it is actually a loss of dopamine producers in the brain which result in a less control of muscle movements.
Today, I wanted to find out what research advancements have occurred since I last explored this area. I have found that many researchers think that environmental factors may play a big role in the development of Parkinson's Disease. This particular paper (http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1002237) set out to prove that coffee had an effect on the chance one had of getting Parkinson's. However, they found that one had to have a variation in the glutamate-receptor gene GRIN2A, a gene that is involved with regulating motor control, and be a heavy coffee drinking in order to increase one's chances. Evidence that they believe to prove it is not just genes or environment but both working together that produce PD. Note that they do not say that if one does not have this variation and is not a heavy coffee drinker one will not get PD, they are saying one has a lesser chance.
These researches did the study multiple times and reduced their participants to just heavy and light (no mediums) in order to achieve their findings. I am still a little skeptical on what they believe they have found. I think that it might just be a coincidence or that one of their two conditions is the real culprit. However, if they did, in fact, discover something very important about either the relation of a certain gene to developing this disease, or the link to coffee (or perhaps the combination of the two) like they believe, then I hope a cure is soon underway.