This study investigates the effect of Internet-delivered Acceptance and Commitment Therapy (IACT) for individuals with Post-Traumatic Stress Disorder (PTSD) and chronic pain. PTSD is a mental health condition that can occur after experiencing or witnessing a traumatic event. Chronic pain is long-lasting pain that persists beyond the usual recovery period or accompanies a chronic health condition. The study involves a randomized controlled trial where participants are either assigned to receive IACT or placed on a waitlist before receiving the same treatment.

Participants will undergo several assessments throughout the study. Initially, they will complete pre-treatment assessments, including the Clinician-Administered PTSD Scale for DSM-5 and the Mini International Neuropsychiatric Interview to confirm eligibility. During the treatment phase, participants will engage with the internet-based program and complete self-report measures. Post-treatment, participants will provide feedback on their experience and satisfaction with the program. Follow-up assessments will be conducted 3 months and 12 months after treatment to monitor long-term outcomes.

• Who can participate: Adults who have experienced a single traumatic event, have chronic pain interfering with daily life, and can understand Swedish are eligible. Participants must have stable medication doses, access to the internet, and the ability to participate in the rehabilitation process for about 5 hours weekly.
• Study details: Participants will be randomly assigned to either receive IACT immediately or be placed on a waitlist for 12 weeks before starting the therapy. During the study, they will complete various assessments and provide feedback on the therapy's credibility and their experiences.