The emergence of potential treatments to slow the progression of idiopathic Parkinson's disease (PD) has increased the need for early identification of persons at risk. Although considered controversial, some prior studies indicate that PD patients may have premorbid histories of greater trait introversion or shyness as well as increased rates of disorders associated with shyness (e.g., anxiety, affective disorders, and irritable bowel syndrome). Essential features of trait shyness include (a) inhibited and avoidant behaviors and (b) physiological hyperreactivity to the novel or unfamiliar. In parallel, (a) depression in PD patients is associated with increased harm avoidance (a possible serotonergic function), and (b) PD patients have premorbid and comorbid decreases in novelty-seeking (a possible dopaminergic function). Taken together, previous research suggests the following hypotheses: (1) given evidence for marked heritability of shyness, shy elderly should report higher rates of PD in their family members than would nonshy elderly; and (2) shy elderly without PD should exhibit psychological and biologic characteristics similar to those reported in PD. Two groups, representing the top 27% (n = 37) and bottom 31% (n = 43) of scores on a standardized shyness scale, were drawn from a larger cohort of 138 older adults (ages 50-90) living in an active retirement community. Seventeen percent of the shy versus 2% of the nonshy reported PD in a family member or self (P < .05). Shy elderly were significantly more anxious (P < .01) and depressed (P < .05) than were the nonshy. Shy subjects rated themselves significantly higher on feeling ill from the odor of environmental chemicals (pesticide, car exhaust, paint, perfume, new carpet) than did the nonshy group. In a separate study of non-PD patients, depressed elderly with self-reported childhood shyness in themselves (n = 7) showed higher levels than did depressed elderly without childhood shyness (n = 7) of plasma L-cysteine (P = .05), the sulfurated amino acid previously shown to be elevated in PD patients, as well as of post-dexamethasone plasma cortisol (P < .05). The findings support the hypotheses and suggest the need for additional investigation of the neurobiology of trait shyness as a possible risk factor for PD.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Geriatric Psychiatry and Neurology|
|State||Published - 1995|
ASJC Scopus subject areas
- Geriatrics and Gerontology
- Neuropsychology and Physiological Psychology