PSYCHOLOGICAL CHARACTERISTICS AND SUBJECTIVE INTOLERANCE FOR XENOBIOTIC AGENTS OF NORMAL YOUNG-ADULTS WITH TRAIT SHYNESS AND DEFENSIVENESS - A PARKINSONIAN-LIKE PERSONALITY TYPE

The present study examines the psychological characteristics and self- reported responses to xenobiotic agents such as tobacco smoke and pest icide of normal young adults with personality traits similar to those claimed for Parkinsonian patients. Previous research, though controver sial, has suggested that persons with idiopathic Parkinson's disease ( PD) have premorbid personality traits that may include shyness and rep ressive defensiveness. Other epidemiological evidence indicates that P D patients may have premorbidly increased prevalence of anxiety, affec tive, and/or somatoform disorders; decreased rates of smoking and alco hol consumption; and elevated exposure to herbicides or pesticides. A total of 783 college students enrolled in an introductory psychology c ourse completed the Cheek-Buss Scale (shyness), the Marlowe-Crowne Soc ial Desirability Scale (defensiveness), Symptom Checklist 90 (revised) , the Mastery Scale, a health history checklist, and rating scales for frequency of illness from alcohol and 10 common environmental chemica ls. Subjects were divided into four groups on the basis of above- vers us below-median scores on the Cheek-Buss and Marlowe-Crowne scales (pe rsons high in shyness and defensiveness, those high only in shyness, t hose high only in defensiveness, and those low in both shyness and def ensiveness). The group high in shyness but low in defensiveness had th e highest, whereas the group low in shyness but high in defensiveness had the lowest, total scores on the SCL-90-R; the two shyest groups we re lowest in sense of mastery. Similar to PD, the group high in both s hyness and defensiveness overall reported the least number of smokers (10% vs. 19% in those high only in shyness, 17% in those high only in defensiveness, and 28% in those low in both traits, p <.001); differen ces within women largely accounted for this finding. Subjects higher i n shyness and/or defensiveness rated themselves higher in frequency of illness from a small amount of alcohol than did those who were low in both shyness and defensiveness. The group who was high in both shynes s and defensiveness tended to report the highest frequency of illness from pesticide as well as other xenobiotic odors (e.g., newsprint). Ta ken together with previous research, the findings suggest that certain young adults high in shyness, and especially those also high in defen siveness, may be among the subset of the population at increased risk for PD later in life.