Psychological Intervention for Fatigue in Inflammatory Bowel Diseases

The investigators would like to evaluate the effect of a multicomponent psychological treatment on fatigue as a symptom of patients with inflammatory bowel diseases (IBD). The intervention will be a combined program consisting of a psychological intervention (Acceptance and Commitment Therapy) and a behavioral intervention (implementation of frequent short naps and graded increase of physical activity). Next to the hypothesized effect on fatigue, the investigators will also measure the effect on fatigability, IBD related disability, anxiety, depression, stress, disease acceptance and perceived control as well as (biomarkers of) disease activity.