BackgroundOvarian hormones have been implicated as a potential source of variability in the effectiveness of exposure therapy for anxiety disorders in women. Additionally, preclinical studies in healthy women indicate that ovarian hormones are related to cognitive modes of emotion regulation, like cognitive restructuring. The purpose of the current study was to determine whether a relationship exists between endogenous ovarian hormones and the outcomes of cognitive restructuring in clinically anxious women. MethodsNinety women with spider phobia received training in cognitive restructuring or a control task and provided a blood sample for the measurement of serum estradiol and progesterone levels. Behavioral avoidance, using a behavioral approach task with a live spider, and self-reported fear of spiders were measured at baseline and 1-week post-treatment. ResultsThe results indicated that heightened levels of progesterone, but not estradiol, at the time of cognitive restructuring predicted greater post-treatment reductions in behavioral avoidance, but not self-reported fear, amongst women who received cognitive restructuring but not those in the control group. LimitationsAs menstrual cycle phase was not assessed; the present study provides information regarding how the benefits of cognitive therapy are predicted by between-person individual differences in absolute hormone levels, but does not examine the relationship between within-person fluctuations in hormone levels and outcomes. ConclusionsThese results suggest the effectiveness of cognitive therapy for anxiety disorders in women may differ depending on endogenous levels of progesterone, and raise the possibility that progesterone could be a useful pharmacological adjunct to cognitive therapy.