A single administration of testosterone reduces fear-potentiated startle in humans

Background: Ample evidence from animal research indicates that the gonadal steroid hormone testosterone has fear-reducing properties. Human data on this topic, however are scarce and far less unequivocal. The present study therefore aimed to scrutinize anxiolytic effects of a single dose of testosterone, using a direct physiological index of fear in humans. Methods; Twenty health female participants were tested in a double-blind. placebo-controlled crossover design involving sublingual administration of a single close of testosterone. Four hours after intake we assessed effects on baseline startle and fear-potentiated startle in a verbal threat-of-shock paradigm. Results: In accordance with predictions, testosterone administration resulted in reduced fear potentiated startle. without affecting baseline startle. Conclusions: This study provides direct evidence that a single close of testosterone reduces fear in humans. The relationship of this effect to previous research on anxiolytic effects of benzodiazepines, as well as possible mechanisms of action, is discussed.