Methods 150 patients aged 18 years and older can self-refer through a web-page to apply for participation. Before inclusion patients will undergo a video-diagnostic interview. Patients are randomly assigned to 12 weeks of either, 1) active treatment: consisting of internet-based ACT (iACT) with 7 therapist-guided modules of self-help text, exercises, patient videos and audio-files, or 2) active control condition: consisting of an internet-based discussion forum (iFORUM) with 7 topics of discussion.