Personality traits and brain dopaminergic function in Parkinson's disease

A distinctive personality type, characterized by introversion, inflexibilit y, and low novelty seeking, has been suggested to be associated with Parkin son's disease. To test the hypothesis that Parkinson's disease is associate d with a specific dopamine-related personality type, the personality struct ures of 61 unmedicated Parkinson's disease patients and 45 healthy controls were examined. Additionally, in 47 Parkinson's disease patients, the dopam inergic function in the brain was directly measured with 6-[F-18]fluoro-L-d opa (F-18-dopa) positron emission tomography (PET) with MRI coregistration. The novelty-seeking personality score, supposedly associated with the park insonian personality, was slightly lower in the Parkinson's disease group c ompared with controls, but it did not have a significant relationship with F-18-dopa uptake in any of the brain regions studied (r = -0.12 to 0.11, P > 0.15). The harm-avoidance personality score, associated with anxiety and depression, was clearly increased in patients with Parkinson's disease and it had a paradoxical, highly significant positive correlation with the F-18 -dopa uptake in the right caudate nucleus (r = 0.53, P = 0.04, Bonferroni c orrected for 220 comparisons). Although the results of this study are not i n disagreement with the concept of low-novelty-seeking personality type in Parkinson's disease, the personality type does not seem to be dopamine depe ndent. The correlation between the personality trait of harm avoidance and F-18-dopa may reflect a specific feedback circuitry of neurotransmitters th at is associated with negative emotionality in Parkinson's disease.