In the first years of the Parkinson's disease, the symptoms can be controlled by dopamine-replacement therapy. Nevertheless, as the disease process continues the effectiveness of treatment is progressively lost, with patients experiencing considerable swings in their movement ability, from complete stiffness, to short periods of controlled movement, and uncontrolled, unwanted movement. A considerable number will also develop dementia in time. The economic consequences for local authorities and the State are therefore considerable.

So far, 2-4% of Parkinson's disease cases have been found to have a genetic cause, suggesting that the disease can start for a number of different reasons that ultimately affect the same biochemical mechanisms. The degree to which genetic predisposition and/or environmental factors affect the development of the disease remains to be established. However, mutations identified in specific proteins are now providing important insight into disease mechanisms and will result in novel therapies aimed at halting disease development.