Trajectories of change in pediatric functional abdominal pain disorders during Internet cognitive behavior therapy: A single case experimental study.

Functional abdominal pain disorders (FAPDs) are prevalent in youth and affect daily life. Therapist-supported Internet-delivered cognitive-behavioral-therapy (ICBT) is promising, though the detailed trajectories of therapeutic effects unknown. This study aimed to analyze trajectories of effect and timing of changes in abdominal symptoms (primary outcome) and psychological factors (catastrophizing, avoidance and control behavior, pain acceptance (secondary outcomes)) in children and adolescents during 10 weeks of exposure-based ICBT for FAPDs in a randomized multiple-baseline single-case experimental design study in six children and six adolescents with FAPDs, referred from pediatric departments. Outcomes were assessed daily during baseline (A), treatment (B1: Main treatment components, B2: Training repeated exposures), and three-month follow-up (C). Effects were evaluated with visual analyses, Tau-U effect sizes for each individual, and multilevel modeling for group-level effects. All participants completed all treatment modules. Individually, treatment effectively reduced abdominal symptoms in half of the participants at three-month follow-up, following diverse trajectories with varying sequences of secondary outcome changes. At group-level, children demonstrated significant effects on estimated means of all outcomes at follow-up (P<0.05), while adolescents did on all outcomes (P<0.05) except one pain acceptance item (pain control). The group trajectories differed: children showed significant daily changes in abdominal symptoms during treatment B2, while adolescents exhibited significant slopes in most outcomes except one pain acceptance item (pain control) as early as during treatment B1. The findings support the effect of ICBT for FAPDs in youth, although with varying effect trajectories and differences in the timing of outcome changes across individuals and age-groups. PERSPECTIVES: This study provides evidence for the effect of ICBT in managing FAPDs in children and adolescents while uncovering individual and age-related differences in trajectories of changes in abdominal symptoms and psychological factors. Clinicians and researchers can use these findings to refine treatment protocols and explore mechanisms underlying these variations. CLINICAL TRIAL PREREGISTRATION: NCT05237882.