June 23, 2009 — A new study has shown no link between either high or low novelty-seeking personality traits exhibited in younger years and the risk of developing parkinsonism or Parkinson's disease (PD) later in life.
For decades, there has been speculation that there may be a distinctive "parkinsonian personality" associated with an increased risk for the disease. According to this theory, a person at risk for eventually developing Parkinson's disease is morally rigid, introverted, punctual, cautious, and conventional. However, results of the new study show no association between PD development and the presence of either with high or low novelty-seeking traits.
"We provided the first evidence that it's not possible to recognize people at risk of Parkinson's disease many years before they develop the disease itself on the basis of their personality traits," said Gennarina Arabia, MD, from the Mayo Clinic in Rochester, Minnesota and the Institute of Neurology at the Università degli studi Magna Græcia di Catanzaro, in Italy, who led the investigation.
Their findings were presented during the Movement Disorder Society's 13th International Congress of Parkinson's Disease and Movement Disorders, in Paris, France.
Historical Cohort
This study is part of the growing body of research that aims to determine whether personality traits precede PD symptom onset and increase risk for this condition.
Dr. Arabia and her colleagues established a historical cohort of 7216 subjects who completed the Minnesota Multiphasic Personality Inventory (MMPI) at the Mayo Clinic from 1962 through 1965. Of these, 6822 (94.5%) were followed for over 40 years either through phone interviews with the subject or a close relative or by means of archived records or death certificates. During follow-up, 227 patients developed parkinsonism, of whom 156 were diagnosed with PD.
The researchers used 5 MMPI scales (sensation-seeking, hypomania, positive emotionality, constraint, and social-introversion scales) to examine the role of novelty-seeking personality traits in the development of PD. Features of the so-called "at-risk" personality, including moral rigidity, etc, are included in these scales, said Dr. Arabia.
The investigators found no association between sensation seeking and an increased risk for PD. They also found no link between PD and hypomania, positive emotionality, constraint, or social-introversion traits.
"In our study, we investigated the risk of developing PD correlated with all the possible scores of the scales for novelty seeking — from low to high scores," said Dr. Arabia in an email interview. "There was no association with either low or high degree of novelty-seeking personality traits."
While this research has no immediate clinical implications and probably will not result in any new recommendations for physicians, the findings do open new areas of exploration related to the issue of personality and PD, said Dr. Arabia.
Impulse Control
For example, she noted, there is growing interest in studying impulse-control disorders displayed by some PD patients who take dopaminergic drugs. These disorders involve pathological gambling, hypersexuality, compulsive eating, and compulsive buying — behaviors that could have an important social impact, said Dr. Arabia.
"It would be of great interest to investigate the link between the premorbid novelty-seeking personality and the later development of these dopaminergic drug-related compulsive behaviors in PD patients," she told Medscape Neurology.
Dr. Arabia and her colleagues plan to take advantage of their cohort of over 7000 subjects who completed the MMPI and have been followed for over 4 decades to explore the association of some of these other personality traits and PD.
No Definitive Answers
Asked for a comment, Rajesh Pahwa, MD, Laverne and Joyce Rider professor of neurology and director of the Parkinson Disease and Movement Disorder Center at the University of Kansas Medical Center, in Kansas City, said that while the topic is "interesting," the current study does not definitively answer the question of what role personality traits play in PD.
"More prospective studies are required with more vigorous criteria for both the diagnosis of PD and assessing the premorbid personality traits," he said.
Dr. Arabia reports no conflict of interest.
Movement Disorder Society's 13th International Congress of Parkinson's Disease and Movement Disorders, Paris France: Abstract 160. Presented June 8, 2009.
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