Developmental instability predicts individual variation in verbal memory skill after caffeine ingestion

Objective: To determine the mediating effects of developmental instability on individual differences in response to caffeine. Background: Individual v ariation of drug effects might reflect broad genomic factors as well as the direct effects of specific alleles. The current study tested the hypothesi s that individual differences in developmental instability, in part determi ned by genomic characteristics, would predict individual variation in the m agnitude of caffeine-induced verbal memory deficits. Minor physical anomali es and fluctuating asymmetry were used as measures of developmental instabi lity. Method: One hundred participants were (1) administered one version of the Rey Auditory Verbal Learning Test; (2) given a dose of caffeine determ ined by body weight (3 mg/kg); (3) assessed for minor physical anomalies an d fluctuating asymmetry; and (4) given an alternate randomized version of t he Rey Auditory Verbal Learning Test. Results: Consistent with predictions, a composite measure of developmental instability predicted the magnitude o f caffeine-induced memory decrements. Conclusions: These results may have i mportant implications for the genetic underpinnings of individual differenc es in drug effects.