Individual differences in mood reactions to d-amphetamine: a test of three personality factors.

Individual differences in self-reported mood following either 5 mg or 10 mg d-amphetamine challenge were examined in order to test the modifying role of three factors of personality, viz., the Eysencks' psychoticism, Cloninger's novelty seeking, and Depue and Collins' extraversion. In a double-blind study, mood measures (energetic arousal, tense arousal, and hedonic tone) were taken immediately following a single-dose of d-amphetamine and then again after 90 min. The results showed significant psychoticism x d-amphetamine interactions for both drug doses: d-amphetamine increased energetic arousal and hedonic tone, and reduced tense arousal, only in low psychoticism individuals; in high psychoticism individuals, it led to lowered energetic arousal and hedonic tone, and increased tense arousal. Neither novelty seeking nor extraversion modified the effects of d-amphetamine. These data suggest a link between psychoticism and dopaminergic functioning, although they do not rule out the involvement of other transmitter systems (e.g. noradrenergic). In common with other studies, such findings point to the important role that well-established factors of personality play in accounting for individual differences in reactions to psychoactive drugs. It is concluded that the routine inclusion of personality measures in future psychopharmacological studies may help to refine the characterization of drug effects.