The study uses a replicated randomized single case design. Participants were 12 individuals with chronic pain problems and residual problems after undergoing a multimodal pain rehabilitation. They also had comorbid emotional problems. Treatment consisted of 10 weeks of Internet delivered, therapist guided CBT based self-help treatment based on the Unified Protocol.

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.

Participants were 12 individuals with chronic pain problems. The sample consisted of 9 females (75 %) and 3 males (25 %). Participants' age ranged from 30 to 60 (M= 47, sd= 9). See table 1 for further description of the participants. All participants had completed MMR within the past three years.

Participants for the treatment study filled in baseline measurements at between 3 and 10 time points. Baseline measurements were separated by at least five days. In connection with the last baseline measurement, participants filled out pretreatment measurements and started treatment, consisting of 10 weekly modules. Process measurements were filled out once every module, as well as longer measurements at mid- and post treatment. A follow-up was done via the platform after 3 months. Treatment consisted of 10 weeks of internet delivered, therapist guided CBT based self-help treatment based on the Unified Protocol.

Inclusion Criteria:

• Chronic pain problems (duration > 3 months)
• Depressive symptoms and/or anxiety symptoms (> 15 points on the Swedish Montgomery Åsberg Depression Schedule (MDRS-S) and/or > 7 points on the Overall Anxiety Symptoms and Impairment Scale, (OASIS))
• MMR within the last three years
• > 18 years
• Fluent in reading and writing Swedish, and
• Internet access.

Exclusion Criteria:

• Ongoing or planned psychological treatment delivered by a psychologist or a psychotherapist
• Planned surgery
• Suicidality
• Severe depression
• Ongoing alcohol or substance abuse, and
• Ongoing psychosis