The PedsQL is a modular, youth- and parent-report questionnaire assessing health-related quality of life in children and adolescents ages 2 to 18. The PedsQL Generic Core Scales contain 23-items about quality of life in physical, emotional, social, and school domains. Response options are on a five-point scale, ranging from 0 ("never") to 4 ("almost always"). Items are summed and higher scores indicate higher well-being.

The SIQR is used to measure physical function, overall impact of the syndrome, and symptom severity in youth (self- and parent-report). Respondents are asked to rate items on scales such as "no difficulty" to "very difficult" (physical function), "never" to "always" (impact of the syndrome), or "no pain" to "unbearable pain" (example of symptom severity). Total scores range from 0 (indicating no symptom impact) to 100 (extreme symptom impact). A 14% change in scores has been empirically determined to represent minimal clinically significant difference following treatment.

The CGI is a clinician-rated measure that assesses overall severity (CGI-S) and improvement (CGI-I) of child symptoms following treatment. CGI-S scores range from 1 ("normal, not at all ill") to 7 ("extremely ill"). CGI-I scores of 1 ("very much improved") or 2 ("much improved") indicate a positive treatment response; all other responses (3 "minimally improved" to 7 "very much worse") are considered negative responses to treatment.

The SCARED is a 41-item self- and parent-report questionnaire assessing a range of anxiety symptoms. It is appropriate for children and adolescents ages 8-18. Items are rated on a 3-point scale ranging from 0 ("not true or hardly ever true") to 2 ("very true or often true"). Items are summed and total scores above 25 indicate the likely presence of an anxiety disorder.

The CDI-2 is a 28-item questionnaire assessing depressive symptoms. There are child- and parent- report versions. Respondents are asked to rate symptoms they have experienced (or observed, for parents) over the past two weeks. Each item contains 3 statements scored in order of increasing severity from 0 to 2. Higher total scores indicate greater depressive symptoms.

The FASA is a 13-item parent- and child-report scale that assesses family accommodation of a child's anxiety symptoms. The FASA asks respondents to rate the frequency of parental accommodation, the participation of parents in child's symptoms, and the changes that parents make in routines and schedules due to child's somatic symptoms. Items are rated on a 5-point response scale. Together, these items generate the total accommodation score, with higher scores indicating greater frequency and intensity of accommodation. One additional item assesses the degree of distress the accommodation causes the parents/child, and 4 additional items assess the short-term, negative consequences of not accommodating.

The PSI-4-SF is a 36-item parent-report scale that assesses three domains of parenting stress, including Parental Distress, Parent-Child Dysfunctional Interaction, and Difficult Child, which combine to form a Total Stress scale. Items are rated on a 5-point scale ranging from 1 ("strongly disagree") to 5 ("strongly agree"), with higher scores indicating more parenting stress.

The CCQ will be used to assess parent expectancies about treatment. To do so, it will be administered to all parents at the end of the first intervention session, after the treatment rationale has been presented. Parents will be asked to make ratings using a scale of 0 to 2 (None, Some, A lot) about: (1) how logical the treatment seems; (2) how confident they are the treatment will be successful, and (3) how confident they would be in recommending the treatment to a friend.

The ICPACS is a 12-item parent-report measure that assesses the frequency of family accommodation of the child's pain in the past week. Items are rated on a scale ranging from 1 to 5. It includes three subscales: Modifications, Assistance, and Supportive Behaviors. An initial validation study indicated high internal consistency for the total scale (Harrison et al., 2016).

The CRPBI is a 30-item scale used to assess current level of perceived parental behaviors, including acceptance and psychological control. Items are rated on a scale from 1 (Not like…) to 3 (A lot like … my mother). A higher score indicates higher perceived behaviors. There is also a parent-report version of this scale (PRPBI).

The PSS is a 14-item scale that assesses perceived stress of life situations in adolescents and adults. Items are scored on a 5-point scale (0=never to 4=very often). Higher total scores indicate greater levels of perceived stress. The PSS has satisfactory reliability and has well-established validity in relation to physiological stress responses and anxiety and depressive disorders.

The CASI is an 18-item child self-report measure that assesses the extent to which children interpret anxiety symptoms as having negative physical, mental and social consequences. The scale has good construct validity, internal consistency and test-retest reliability (Silverman et al., 1991).

The ARI-C/P is a parent- and child report measure that assesses frequency, duration, and threshold of child irritability symptoms over 6 months. The ARI-C/P contains 6 items that are rated along a 3-point scale (0 = not true, 1 = somewhat true, 2 = certainly true); total scores range from 0-12. A 7th item, not calculated in the total score, assesses level of general impairment caused by the irritability. The ARI-C/P has shown satisfactory internal consistency, discriminant validity, and is adequately described by a one-factor solution in confirmatory factor analyses.