Internet-delivered cognitive behavioural therapy for chronic fatigue among adolescents with a chronic medical condition: a single case study Abstract Background: Severe fatigue is a prominent symptom among adolescents with a chronic medical condition, with major impact on their well-being and daily functioning. Internet-based cognitive behavioural therapy (I-CBT) is a promising treatment for severe fatigue among adolescents with a chronic medical condition, but its effectiveness has not been studied. Aims: We developed an I-CBT intervention for disabling fatigue in a chronic medical condition and tested its feasibility and effectiveness in an adolescent with an immune dysregulation disorder (IDD), namely juvenile idiopathic arthritis (JIA). Method: The application of I-CBT is illustrated through a clinical case study of a 15-year-old girl with JIA and chronic severe fatigue. An A-B single case experimental design was used with randomization of the waiting period prior to start of the intervention. Outcomes were weekly measures of fatigue severity, physical functioning, school absence and pain severity. Results: Fatigue severity significantly decreased following I-CBT. Improvements were observed towards increased school attendance and improved physical functioning following the intervention, but these effects were too small to become significant. Conclusions: The study provides preliminary support for the feasibility and effectiveness of the application of I-CBT for severe fatigue in adolescents with a long-term medical condition. https://www.cambridge.org/core/jour...e-case-study/D451919571B112EE255B6DC00CC78E73 seriously?