Hypnotherapy Through Self-exercises in Children With Functional Abdominal Pain in Primary Care

The goal of this randomised controlled trial is to study the (cost-)effectiveness of home-based hypnotherapy by self-exercises in children with functional abdominal pain (FAP) or irritable bowel syndrome (IBS) in primary care. The main questions it aims to answer are: * What is the effect of home-based hypnotherapy by self-exercises on adequate relief of abdominal pain and discomfort in addition to care as usual of general practitioners (GPs), compared to care as usual of GPs alone in children with FAP or IBS? * What is the effect of home-based hypnotherapy by self-exercises in addition to care as usual by GPs compared to care as usual of GPs alone in children with FAP or IBS on: * Frequency and intensity of abdominal pain and discomfort * Pain severity * Daily functioning and impact * Anxiety and depression * Pain beliefs * Sleep disturbances * School absence * Use of health care services, including GP visits and referrals to secondary care * Costs (healthcare and societal perspective) Participants in the intervention group will receive home-based hypnotherapy 5 times a week for approximately 15-20 minutes a day during 3 months in addition to care as usual by their GP according to the Dutch society of GPs\' guideline for children with abdominal pain. Participants in the control group will receive care as usual by their GP according to the Dutch society of GPs\' guideline for children with abdominal pain.