Inhibition of fear is differentially associated with cycling estrogen levels in women.

BACKGROUND Although the prevalence of posttraumatic stress disorder (PTSD) is twice as high in women as it is in men, the role of estrogen in the risk for PTSD is not well understood. Deficits in fear inhibition and impaired safety signal learning may be biomarkers for PTSD. We examined menstrual cycle phase and serum estradiol levels in naturally cycling women while they were undergoing a novel conditioned inhibition procedure that measured their ability to discriminate between cues representing danger versus safety and to inhibit fear in the presence of safety cues. METHODS Sample 1 included healthy participants in whom we compared inhibition of fearpotentiated startle during the follicular (lower estrogen) and luteal (higher estrogen) phases of the menstrual cycle. We used the same paradigm in a traumatized clinical population (sample 2) in whom we compared low versus high estradiol levels. RESULTS In both samples, we found that lower estrogen in cycling women was associated with impaired fear inhibition. LIMITATIONS In the clinical sample, the low estradiol group was on average older than the high estradiol group owing to the random recruitment approach; we did not exclude participants based on hormonal status or menopause. CONCLUSION Our results suggest that the lower estrogen state during normal menstrual cycling may contribute to risk for anxiety disorders through dysregulated fear responses.