Synthetic Hormone Dose in Hormonal Contraceptives Predicts Individual Differences in Personality

The purpose of this study is to investigate whether the dose of synthetic hormones in hormonal contraceptives (HCs) is related to between-subject variation in personality. HC users reported the brand of their HC and completed the Big Five Inventory (BFI). Each woman’s dose of synthetic hormones was calculated and a median split assigned women to the high or low synthetic estrogen group and the high or low synthetic progesterone group. Women taking HCs high in synthetic estrogen scored lower on extraversion and higher on neuroticism than those taking HCs relatively low in synthetic estrogen. There were no effects of synthetic progesterone level on any of the Big Five personality traits. Results suggest that synthetic estrogen in HCs may influence women’s personality. Future research should investigate this possibility experimentally or using a pre-post design, and should investigate anatomical neural correlates.