The primary scientific objective of the study entails examining whether altered endogenous pain inhibition is present in children with functional abdominal pain (FAP) and irritable bowel syndrome (IBS) compared with healthy controls (Part 1). A secondary objective implies examining whether pediatric pain neuroscience education (PNE) is able to improve pain catastrophizing, pain-related fear, pain intensity (including symptoms and indices of central sensitization) and pain-related functional disability in children with FAP or IBS (Part 2).

Abdominal pain-related functional gastrointestinal disorders (AP-FGIDs) are common in children, showing a prevalence of 13.5% in Western populations and developing countries. Gastrointestinal disorders are categorised within the Rome criteria III, with irritable bowel syndrome (IBS) (65%) and functional abdominal pain (FAP) (35%) as most commonly occurring subtypes, followed by FAP syndrome, functional dyspepsia and abdominal migraine. These numbers call for action, knowing that persistent pain periods associated with AP-FGIDs significantly interferes with a child's daily functioning. Children suffering from AP-FGIDs participate less during recreational activities, show difficulties in maintaining social contacts, are more absent at school and express academic impairments. Additionally, they report decreased health related quality of life and need more health care utilization.

To date, the pathogenesis underlying AP-FGIDs in children remains unclear. Previous studies suggested abnormal brain-gut interaction, altered gut motility, visceral hypersensitivity, psychosocial disturbance and immune activation as possible explanations for the symptoms. In accordance to research in adults with FGIDs evidence is even growing for the contribution of central sensitization (CS) in the development or persistence of AP-FGIDs in children. CS is defined as "an amplification of neural signalling within the central nervous system that elicits pain hypersensitivity" or "increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input". This process encompasses malfunctioning of descending inhibitory nociceptive pathways which result in dysfunctional endogenous analgesic control and increased activity of descending nociceptive facilitation and overactivity of the pain neuromatrix in the brain. A systematic review addressing the contribution of CS in pediatric chronic pain conditions concluded that manifestations such as somatic hyperalgesia and altered central pain processing in children with recurrent abdominal pain disorders (RAP) and deficient descending inhibitory nociceptive processing in girls with irritable bowel syndrome (IBS) are indicative of CS in some subtypes of AP-FGIDs (review in progress). However, given the heterogeneous study populations, different protocols and methods used to objectify the presence of CS in this review, no clear statement could be made. In addition, no study examining descending inhibitory nociceptive processing in children with FAP was found.

Descending inhibitory nociceptive processing might be dysfunctional in children with FAP and IBS. Anyhow, research demonstrated that this manifestation of CS can be further influenced by the child's characteristics. Behavioural responses, emotional and cognitive aspects are involved in the facilitation of sensitization through an increased cerebral activation of limbic structures, the insula and large areas of the frontal, temporal and parietal cortices, resulting in a diminished inhibition of the descending pathways.

Parental behaviours may also play an important role in the child's adjustment to pain. Parents are considered essential participants in the management of their child's pain, as parental attitudes, responses, and beliefs can influence the child's pain and adherence to treatment. Indeed, both parental solicitous behaviours (e.g., according special privileges to the child) and parental discouraging behaviours (e.g., criticizing the child) have been found to be associated with increased functional disability. Further, evidence suggests that children's own pain beliefs and pain coping skills may be modelled after their parents' (maladaptive) pain beliefs and pain coping skills. Additionally, increased levels of parent emotional distress have been linked to higher levels of child functional disability and self-reported pain. This underscores the importance of including parents in the assessment and treatment of pediatric chronic pain for optimal outcomes.

Negative cognitions of both the parents and the child can develop when they do not understand the origin of the FAP or IBS. Based on the premise that a better understanding of the nature of the illness results in improved patient outcomes, both child and parents should be addressed by education. Given the possible contribution of CS in children with FAP or IBS, education should include explanation and reassurance about the cause of pain, a brief summary of relevant pain mechanisms and the integral role of psychosocial and physical factors in precipitating and maintaining pain. This main content can be given by pain neuroscience education (PNE). PNE has been studied in various adult chronic pain populations and has shown to be effective in changing pain beliefs and improving health status as well as pain coping strategies.

In contrast to a traditional model of tissue injury or nociception and pain, PNE aims to describe how the nervous system interprets information from tissues through peripheral nerve sensitization, central sensitization, synaptic activity and brain processing. It also explains how neural activation, as either upregulation or downregulation, has the ability to modulate the pain experience in response to (or in absence of) nociceptive input. Patients are thus educated that the nervous system's processing of their injury, in conjunction with various psychosocial aspects, determines their pain experience and that pain is not always a true representation of the status of the tissues. Up to recently, no studies have examined the benefits of PNE in the context of pediatric chronic pain. Drawing upon available evidence in adult samples, it is expected that PNE provided to children will lead to beneficial child pain-related outcomes. Involving parents in PNE sessions will facilitate increased parental understanding of biopsychosocial factors that influence their child's pain, as well as learn how they can support their child to manage symptoms.

Concrete, the present study will examine (1) the function of descending inhibitory nociceptive processing in children with FAP or IBS compared to healthy children (Part 1) and whether (2) reconceptualization of pain, by PNE, is able to influence pain catastrophizing, pain-related fear, pain intensity (including symptoms and indices of central sensitization) and pain-related functional disability (Part 2).

Inclusion Criteria:

• Informed consent
• > 3 months pain
• diagnosis functional abdominal pain or irritable bowel syndrome

Exclusion Criteria:

• Concomitant organic gastrointestinal disease or chronic disease
• Ongoing specific treatment by another health care specialist (physician or psychotherapist) for abdominal pain symptoms
• Previous pain education or relaxation therapy
• Mental retardation
• Insufficient knowledge of the Dutch language
• Preterm birth
• Menstruation