Sufficient data were obtained for estradiol, progesterone, pregnenolone, 5αDHP, and allopregnanolone to allow for meaningful analysis of impact on cortical GABA levels and/or between-group differences in hormone levels. All variables except 5αDHP were log transformed to eliminate positive skewness. Results for progesterone, estradiol, pregnenolone, and allopregnanolone are given in Table 2. With respect to between-group differences in hormone levels, significant group × phase interaction occurred for pregnenolone (F2,26= 3.7, P = .03), progesterone (F2,25 = 5.0, P = .01), and estradiol (F2,25 = 3.96, P = .03). Between-group differences for these hormones occurred in the late luteal phase (pregnenolone: F1,26 = 7.9, P = .009; progesterone: F1,25 = 10.3, P = .004; and estradiol: F1,25 = 6.77, P = .02), although the late luteal difference in estradiol did not pass the conservative Bonferroni correction. Analysis of between-group difference in 5αDHP levels was limited to the mid luteal phase secondary to limited sensitivity of the assay to detect follicular phase levels. Women with PMDD had significantly higher levels of 5αDHP in the mid luteal phase than healthy controls (F1,12 = 5.3, P = .04).