Procedure
pain
A letter was sent to interested patients with study details and a pain diary to be filled out before the screening session. At the screening, patients were informed about study requirements and screened for in- and exclusion criteria. They provided written informed consent before enrolment in the study and randomization. Patients were informed that they would be randomized to one of two different psychological interventions or a waitlist control group. This should keep participants blinded to the psychological method and intervention content in the comparison group. To keep the research group blinded to intervention assignment throughout data collection, a research assistant, not part of the research group, provided patients with an anonymous id-number used for data collection. The numbers were randomized in blocks of six by another research assistant using a computer-generated randomization list.Questionnaires were sent to participants by postal mail, filled out, and returned. Baseline measurements were obtained during the 2 weeks period prior to treatment start, and post-intervention measurements were obtained during the 2 weeks post-treatment period. At home, patients also completed a 12-week pain diary starting 1 week pre-intervention until 1-week post-intervention. To investigate potential changes in pain processing and sensibility a female doctor carried out a gynecological experimental pain assessment during the 2-week period prior to treatment start and again during the 2 weeks post-treatment. However, the experimental pain assessment was optional and not required for participation (See Fig. Study timeline