Oral contraceptive use and female genital arousal: methodological considerations

Journal of Sex Research, August, 2005 by Brooke N. Seal, Lori A. Brotto, Boris B. Gorzalka

Women's mental sexual arousal post-OCP onset was significantly increased with the erotic film, t(15) = -5.06, p < .001, as were perception of genital arousal, t(15) = -4.95, p < .001, and perception of autonomic arousal, t(15) = -4.93, p < .001. Positive affect significantly increased, t(15) = -3.87, p = .002, and negative affect was unaffected, t(15) = -0.68, p > .05, with exposure to the erotic film. Anxiety did not change in response to the erotic film at post-OCP onset, t(15) = 0.00, p > .05; however, the difference in anxiety change scores from neutral to erotic stimulation across the two time periods was not significant, t(15) = -1.619, p > .05.

Genital and Self-Report Sexual Arousal Correlations

We conducted correlations between genital and self-report measures by computing Pearson product moment correlation coefficients of the percent change scores in VPA and self-reported arousal (mental and perception of genital arousal). We computed analyses separately before and after OCP use. The correlation between VPA and mental sexual arousal before OCP use was statistically significant, r = 0.498, p = .05. However, the correlation of VPA with perception of genital arousal, r = 0.111, p > .05, was not statistically significant.

Following OCP onset, the correlation between VPA and mental sexual arousal remained statistically significant, r = 0.825, p < .001. In addition, the correlation between VPA and perception of genital arousal was now significant, r = 0.568, p = .02. In order to compare pre- and post-OCP correlations statistically, we derived a Fisher z transformation value for each correlation coefficient and subsequently computed a standardized z-score based on the Fisher z transformation scores. These analyses revealed that neither the increase in correlation of VPA with perception of genital arousal (z = 1.369, p = .1706) nor the increase in correlation of VPA with mental sexual arousal (z = 1.629, p = .1032) was significant.

Side Effects of OCP Use

According to the SES, subjects retrospectively reported experiencing a mean of 2.6 (SD = 1.8) out of a possible 13 physical and emotional side effects over the previous six weeks that they attributed to the OCP. The most common side effects were weight gain (n = 8) and breast tenderness (n = 6). Other side effects reported included nausea (n = 5), headache (n = 5), irritability (n = 4), fatigue (n = 4), emotional lability (n = 2), acne (n = 2), and leg pain (n = 1). Reports of sexual side effects on the SES varied markedly. Five women reported experiencing decreased sexual desire, 5 reported increased sexual desire, and 6 reported no change in their sexual desire. Three participants reported decreased lubrication, 2 reported increased lubrication, and 11 reported no change in lubrication. Two women reported an increase in pain during sexual intercourse, 13 subjects reported no change, and one woman did not respond. Three participants reported a decrease in mental sexual excitement when with a partner, 4 reported an increase in mental sexual excitement, 8 reported no change in mental sexual excitement, and one did not respond.

DISCUSSION

This study examined the effects of oral contraceptive use on genital arousal response as measured by the VPE Overall, the significant increase in VPA that was found at time 1 was absent at time 2 after OCP onset; however, closer examination of individual responses suggests that the significantly higher variability of responses after OCP onset masked an effect. Prior to OCP use, there was an overall significant increase in VPA with the erotic film, and consistent with female sexual psychophysiological studies in general, only 2 women failed to show a VPA increase with the erotic film. However, after OCP onset, 4 women responded with a decrease in VPA to the erotic film, despite an overall significant increase in subjective sexual arousal with the erotic film. Furthermore, exploring the degree of percentage increase in VPA following and prior to OCP onset highlights significant variability of responses. Whereas the range of percentage increase was from 1 to 204% prior to OCP use, the range doubled following OCP onset from 2 to 573%. We believe that this marked variability of VPA responses, including the fact that there were 4 non-responders, accounts for the failure to detect a significant effect of the erotic stimulus on physiological arousal.