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As has already been said, it is still not known what causes Parkinson’s disease, but research has led to some theories, which shed at least some light on the disease.

Recently, scientists have discovered that certain families may be more likely than others to develop Parkinson’s disease because of an abnormality in their genes. The main evidence for this comes from research done on a large Italian family in which many members developed the disease. Tests on their chromosomes revealed an abnormality in chromosome 4 that could be passed on to future generations. However, the presence of this genetic abnormality did not necessarily mean that the disease would develop in all members of the family. What complicates the picture still further is that this abnormality is not necessarily present in other families where the disease affects more than one member, or in isolated cases of the disease. Unfortunately, there is as yet no test that allows doctors to find out if a person is going to develop the disease or not.

In the mid 1980’s some intravenous drug users in America were trying to make a drug called meperidine and accidentally produced a toxic substance called MPTP, which when injected caused them to rapidly develop the signs and symptoms of Parkinson’s disease. This led many people to believe that the disease is caused by a similar toxin (poison) found in the environment or in food. Research into this is still going on, but a link has never been proven. If a toxin is the cause, it is unlikely to be a modern one, since the disease itself has been around for so long. On the positive side, however, this incident did give scientists a method of inducing the signs and symptoms of Parkinson’s disease in the laboratory, which has benefited research into the treatment of the disorder.

It is likely that Parkinson’s disease is caused by a combination of these factors. A particular genetic make-up may make a person more likely to get the disease if they come into contact with certain, as yet unidentified, toxins or environmental triggers. However, if a person who does not have this genetic make-up comes into contact with the same toxin or trigger, they could also go on to develop the disease. In short, particular genetic profiles appear to increase the chances of developing the disease, but not by a great deal.

Researchers have found no viral or bacterial cause for the disease, so on present evidence we can say that it is not infectious. It is also not fatal. Severe stress or anxiety do not cause Parkinson’s disease, but states of severe anxiety, alcoholism, thyroid disease and a variety of rare metabolic and structural disorders, can mimic some of the signs and symptoms of the disease. Doctors carry out tests to rule these disorders out before making a diagnosis of Parkinson’s disease.