THURSDAY, Feb. 16, 2006 (HealthDay News) -- Specific personality traits might boost the risk for Parkinson's disease, British researchers report.
A more cautious, risk-averse approach to life may be linked to increased odds for the motor neuron disease, says a team reporting in the February issue of the Journal of Neurology, Neurosurgery and Psychiatry.
"This study raises the possibility that there is a neurobiological link between low sensation-seeking traits which might underlie the parkinsonism personality," the researchers wrote.
And because more reserved types are less likely to smoke, the finding could throw water on the notion that smoking somehow protects against Parkinson's disease, the researchers added.
In fact, the study was undertaken not primarily to look at personality but to examine the effects of tobacco, alcohol and caffeine on the condition, explained Dr. Andrew H. Evans, who worked on the study while in England and now is a neurologist at the Royal Melbourne Hospital in Australia.
"Over the past 10 to 15 years, there has been an abundance of evidence linking smoking, coffee and alcohol intake as a protective factor," Evans noted.
Investigating further, researchers at the Reta Lila Weston Institute of Neurological Studies in London examined the drinking and smoking habits and consumption of caffeine of 106 people with Parkinson's disease and 106 unaffected individuals.
They also compared participant answers from three standard personality tests measuring depression, anxiety and the willingness to seek sensational experiences.
As expected, the Parkinson's patients drank less, smoked less and consumed less caffeine-containing beverages -- not a surprising finding, since earlier studies have found the same thing, leading some neurologists to speculate that smoking might protect against the disease.
The more striking finding was that the people with Parkinson's disease scored higher on the tests for anxiety and depression and lower on the sensation-seeking test.
They suggest several explanations for the link, including the possibility that shyer, more cautious folks are more vulnerable to Parkinson's disease.
A different explanation is offered by Dr. Kevin Black, a professor of psychiatry, radiology and neurobiology at Washington University in St. Louis, who has been doing work along the same line, using brain scans in addition to testing.
"My personal hunch is that it's more likely that whatever ends up producing parkinsonism starts very early in life," Black said. "When it is mild, it can affect personality -- how much you can be addicted to, or be able to quit, something. Then as it progresses, it affects nerve endings. It makes you more likely to be exposed to whatever causes parkinsonism."
Parkinson's disease is a progressive condition that usually is seen in older persons. It often starts with a slight tremor of one arm, leg or hand, then moves to the rest of the body, causing constant trembling, difficulty in walking and shaking of the head, among other symptoms.
That there is a "Parkinson's personality" has been evident for some time, Black said, "Anecdotally, and then with increasing evidence, that people who develop Parkinson's disease have a more straight-laced personality. When they come to clinic appointments they are always on time, they are law-abiding types."
The British study is valuable because it looks at all the factors believed to be involved in parkinsonism, including cigarette smoking, caffeine and personality traits, Black said. One result of the study is to strike down one postulated positive effect of smoking, he said.
"People have looked for evidence of some good things in tobacco," Black said. "This makes it seem a little less likely."
The study "raises questions rather than answers them," Evans noted. Neurologists studying Parkinson's disease now "maybe must take into account more complex factors, such as personality," he said. But it does weaken the theory that smoking can protect against parkinsonism, he added.
More information
Find out more about Parkinson's disease at the U.S. National Library of Medicine.
