A large healthy-volunteer study linked personality traits to different subjective amphetamine responses. Physical fearlessness was associated with greater arousal, while reward sensitivity was associated with greater euphoria. Feeling stimulated and feeling euphoric were distinct outcomes.
White and de Wit analyzed 286 healthy adults aged 18–35 years. Participants completed four sessions involving placebo and 5, 10 and 20 mg d-amphetamine. Mood and physiological measures were monitored before dosing and for four hours afterward.
Personality was assessed with the Multidimensional Personality Questionnaire Brief Form. Participants in the top and bottom thirds of selected trait scales were compared. Drug conditions were experimentally manipulated; personality traits were measured rather than assigned. The sample was restricted to people of European ancestry for the larger genetics project.
The investigators used principal-components analysis to organize multiple subjective measures into euphoria, arousal and dysphoria factors. High physical fearlessness was associated with greater arousal, and high reward sensitivity with greater euphoria. Greater trait impulsivity, represented by lower Control scores, was associated with greater euphoria and arousal.
These factor-level findings do not mean that every questionnaire item, every trait or every dose showed the same relationship. They also do not demonstrate that a person who feels more aroused performs better on a cognitive task. The outcomes here primarily concerned reported experience after the drug.
The healthy, young and ancestry-restricted sample limits generalization. Comparing extreme thirds can make group contrasts clearer while leaving uncertain how well a model predicts responses throughout the full trait distribution. Multiple related scales and derived factors also require attention when comparing results across studies using different personality instruments.
The study did not follow participants to determine who later developed a substance-use disorder. A proposed vulnerability pathway is therefore different from a validated personal risk prediction. Personality scores and subjective drug ratings likewise cannot replace evidence about exposure, observed functioning or impairment at a particular incident.
Read our analysis of personality traits and amphetamine-evoked dopamine in a different study.
Personality and the acute subjective effects of d-amphetamine in humans. doi:10.1177/0269881112472564.