Study Refines Parkinson's 'Personality' Traits
Risk avoidance seems to mark chemical disorder
MONDAY, Oct. 29, 2001 (HealthDayNews) -- The chemical disorder in the brain that causes symptoms of Parkinson's disease appears to affect a patient's personality, a Finnish study finds.
The finding appears to refine the century-old theory of a distinctive "Parkinsonian personality" characterized by compulsive behavior, inflexibility, introversion and avoidance of new things and experiences, say researchers at the University of Turku.
Their study, which combined a personality questionnaire and high-tech measurements of brain activity, finds a significant difference in harm-avoiding behavior between Parkinson's patients and persons without the condition, says a report in the Nov. 6 issue of the Proceedings of the National Academy of Sciences.
"This is a very interesting finding," says Dr. Marcus E. Raichle, professor of radiology and neurology at Washington University School of Medicine, who edited the report. "It doesn't settle any issues, but it does provide much-needed data in beginning to understand the differences in people's behavior."
Parkinson's disease is caused by the gradual deterioration of nerves in a part of the brain called the substantia nigra, which controls movement. As the nerves die, there is decreased production of dopamine, a brain chemical that transmits signals between nerves, causing tremors, rigidity and other movement problems.
The "Parkinsonian personality" theory arose because dopamine is believed to play a role in the behavior trait called novelty seeking, the Finnish researchers say. And while some studies have supported that theory, they have included only a small number of Parkinson's patients who are taking medication for the condition, which clouds the results.
The Finnish study included 61 Parkinson's patients who were not taking medication and 45 persons without the disease. They all filled out a questionnaire, developed at Washington University, designed to measure personality traits. The Parkinson's patients scored lower on the novelty-seeking scale and higher on the harm-avoidance scale than people in the control group.
The researchers then used positron emission tomography to measure dopamine activity in specific brain centers. They found no relationship between dopamine activity and the low novelty-seeking scores, but the harm-avoidance personality score, which is associated with anxiety and depression, was related to dopamine activity in the right caudate nucleus, a brain center involved in behavior.
"It is possible that there is a unique disturbance of circuitry in Parkinson's disease that could explain the paradoxical, highly significant relationship between harm avoidance and dopaminergic function in the caudate," the researchers write.
It's best to be cautious about that conclusion, Raichle says. "You can't go from involvement of the right caudate to a strict mechanistic connection like harm avoidance," he says. But the finding does indicate the need for more research on the possible connection, he says.
"When someone comes along and finds such a very significant correlation, it offers the possibility of focusing your research," Raichle says. "It's not likely that this can occur by accident."
What To Do
More research is needed into this phenomenon before anything is settled.
For information about Parkinson's disease, go to the National Institute of Neurological Disorders and Stroke or the American Parkinson Disease Association.