Personality and the subjective effects of acute amphetamine in healthy volunteers

Individual differences in the positive mood and other subjective effects of d-amphetamine have been linked to personality traits related to sensation seeking. The current study extends these associations to separate personality traits of reward sensitivity, physical fearlessness, and impulsivity. A total of 128 healthy volunteers received oral doses of d-amphetamine (10 and 20 mg) or placebo in counterbalanced order. Their responses to the drug were measured using the Profile of Mood States, Addiction Research Center Inventory, and Drug Effects Questionnaire. Participants completed the Multidimensional Personality Questionnaire Brief Form to assess personality traits related to reward sensitivity (Agentic Positive Emotionality and Social Potency (SP)), physical fear (Harm Avoidance (HA)), and impulsivity (Control (CL)). Participants were rank ordered on each trait, and individuals with scores in the top and bottom thirds of scores on each trait were compared using ANCOVA. High trait physical fearlessness (low HA) was associated with greater positive activational effects of 10 mg d-amphetamine. High trait reward sensitivity (high SP) was marginally associated with greater positive activational effects of 20 mg d-amphetamine. High trait impulsivity (low CL) was unrelated to positive drug effects in response either dose. The two separate personality traits of physical fearlessness and reward sensitivity are associated with d-amphetamine effects on mood in healthy volunteers. Implications for the vulnerability to psychostimulant addiction in healthy nonaddicts are discussed.