BDNF and endometriosis: In the final revised model, the eight variables discussed above were considered: CA125, BDNF and the six clinical variables, i.e., record of previous surgery to examine for endometriosis, painful periods as a symptom leading to referral for endometriosis, the severity of menstrual pain during last cycle, age at first experience of intercourse pain, age at first regular use of painkillers and age at first diagnosis of ovarian cyst.