BDNF and endometriosis: The Spearman rank correlation coefficient for the association between BDNF mRNA expression in the eutopic endometrium of the endometriosis group and the dysmenorrhoea VAS score was r = 0.52, demonstrating that there was a moderate positive association between BDNF expression in the eutopic endometrium and dysmenorrhoea VAS score (P < 0.05); however, there was no association between BDNF expression in ovarian endometriotic lesions and the dysmenorrhoea VAS score (P > 0.05).