The current study utilized personality measures thought to relate to noradrenergic and catecholamine function (i.e., sensation seeking, anxiety and aggression) to investigate individual differences in amphetamine-induced increases in cortisol. The goal of the study was to better understand variations in responses to psychostimulants in healthy volunteers.
Method: A placebo-controlled within-subjects investigation of salivary cortisol responses to oral D-amphetamine (20 mg) was conducted in seventy (N=70) young adults. Personality traits were assessed using the Eysenck Personality Inventory (EPI), Sensation Seeking Scale Form V (SSS-V) and the Multidimensional Personality Questionnaire-Brief Form (MPQ-BF).
Results: A more rapid rise in salivary cortisol after d-amphetamine was associated with SSS-V Thrill Seeking (r=-0.32 with time to peak, p<0.05). A greater peak increase in cortisol and a greater recovery after amphetamine was positively associated with MPQ-BF Aggression (r=+0.35, p<0.05; r=+0.38, p<0.05). In contrast, cortisol responses were unrelated to a composite measure of trait anxiety (EPI/MPQ-BF Anxiety Index).
Conclusions: The findings suggest that the personality traits of aggression and thrill seeking are related to cortisol responses to d-amphetamine, raising the possibility that personality may predispose certain individuals to use drugs through a glucocorticoid pathway. The data also suggest a distinction between fear and anxiety, as amphetamine-induced cortisol responses were associated with measures of trait fear but not measures of trait anxiety in the current sample.