Table 5.

Analgesic Z-Scores^* for Morphine, Mean (SD)

	NOC women (n=14)			OC women (n=18)
	Follicular	Luteal	Cohen’s D	Follicular	Luteal	Cohen’s D
Heat Pain	−0.24 (0.70)	0.01 (0.60)	−0.38	0.19 (0.78)	−0.006 (0.99)	0.22
Pressure Pain	−0.04 (0.77)	0.16 (0.63)	−0.29	0.03 (0.66)	−0.013 (0.88)	0.06
Ischemic Pain	0.26 (1.29)	−0.05 (1.18)	0.25	−0.20 (0.67)	−0.04 (0.86)	−0.21

A Group X menstrual cycle effect emerged for morphine analgesia on ischemic pain [F(1,29)=6.18, p=0.019]. There was a significant cycle phase effect among NOC women [F(1,13)=12.62, p = 0.004]. Bold indicates significant menstrual cycle phase differences. The significant menstrual cycle effect for morphine ischemic analgesia may be surprising, given the small effect size for this difference. This occurs because the F statistic corrects for correlation between the two repeated measures, and because this correlation is higher for ischemic than heat or pressure pain, a smaller effect is found to be statistically significant (i.e. with higher correlation, there is greater statistical power).

^*Higher scores reflect greater analgesia.