The study uses a replicated randomized single case design. Twelve participants were recruited from three pain clinics and five primary care centers in different municipalities in central Sweden. The clinics and care centers provided addresses and sent a total of 600 letters with information regarding the study to patients who had completed a multimodal pain rehabilitation (MMR) at their facility within the last three years. Participants were also recruited via the Internet through an advertisement on Google Ads that was visible for two months. No reward was offered for taking part in the study. Potential participants were screened and provided demographic information on a secure internet based platform. Afterwards all screened individuals received a telephone call. Excluded individuals were informed about the reason for exclusion and given recommendations regarding alternative treatment options when indicated. Eligible participants were screened further using selected parts of the Mini International Neuropsychiatric Interview. They were also given more information about the study and invited to ask questions. Individuals who met selection criteria were randomized in blocks of four using randomizer.org and half participated in an initial pilot study while half participated in the treatment study reported here. Participants for the treatment study were thereafter randomized to either a short (five week) or a long (10 week) baseline as well as separately randomized to one of five therapists. Therapists were two clinical psychology students in their last year of training, one graduated clinical psychologist, one postgraduate clinical psychology fellow and one certified clinical psychologist. Participants gave written informed consent by sending in a form included in the initial information letter.