Examining Antidepressant Side Effect Burden in Youth: The FIBSER-C Scale in the Texas Youth Depression and Suicide Research Network Study.

Introduction: Evaluating antidepressant side effects in children and adolescents is important, as side effects can significantly impact treatment adherence and outcomes. While there are tools to assess side effects globally encompassing various body systems, their administration time can be substantial, limiting their practical use in clinical settings. This is especially challenging in pediatric practice, where providers need to collect information from both patients and guardians. The Frequency, Intensity, Burden of Side Effects Rating-Child (FIBSER-C) was developed to address this need and assesses side effect frequency, intensity, and burden; however, its psychometric properties have not been examined in pediatric samples. Methods: The analytic sample included n = 746 youth among the first 1000 participants who completed FIBSER-C and were taking antidepressant medication(s). The construct validity of FIBSER-C was examined by confirmatory factor analysis; internal consistency was evaluated using Cronbach's alpha (α); convergent and divergent validity were assessed by examining its association with depression severity and functioning measures. Results: FIBSER-C showed a single-factor structure, with standardized item loadings of 0.73, 0.83, and 0.89. The scale showed good internal consistency (Cronbach's α = 0.85). The FIBSER-C total score was weakly and positively associated with total PHQ-A, Patient-Reported Outcomes Measurement Information System (PROMIS)-Pain, PROMIS-Pain Severity, and PROMIS-Fatigue and was weakly and inversely associated with PROMIS-Physical Function. Conclusions: The FIBSER-C had has good internal consistency and a single-factor solution. The associations between side effect burden and depression severity, as well as functioning domains, were weak. Further research should explore the consistency and stability of the scale over time.