A semi-structured interview for the dimensional assessment of internalizing and externalizing symptoms in children and adolescents: Interview Version of the Symptoms and Functioning Severity Scale (SFSS-I)

Abstract Background This study evaluates the psychometric properties of the newly developed semi-structured interview, Interview Version of the Symptoms and Functioning Severity Scale (SFSS-I), which is designed to provide a dimensional assessment of internalizing and externalizing symptoms. Methods Multi-informant baseline data from the OPTIE study was used, involving 358 children and adolescents aged 6 to 17 years (M = 11.54, SD = 3.4, n = 140 [39.1%] were female). Participants were screened for internalizing and externalizing symptoms. For validity analyses, caregiver (Child Behavior Checklist), youth (Youth Self Report), and teacher ratings (Teacher Report Form) were used. We performed Receiver Operating Characteristic (ROC) analyses to evaluate the effectiveness of the SFSS-I subscales in distinguishing between children and adolescents diagnosed with internalizing and externalizing disorders, as determined by clinical judgement in routine care. Results Confirmatory factor analyses supported a correlated two-factor model for internalizing and externalizing symptoms. Acceptable to good internal consistencies (α = 0.76 to 0.89; ω = 0.76 to 0.90) and excellent interrater reliability on the scale level (ICC ≥ 0.91) was found. The ROC analyses showed an acceptable accuracy in identifying internalizing diagnoses (AUC = 0.76) and excellent accuracy for externalizing diagnoses (AUC = 0.84). Conclusion The SFSS-I demonstrates potential as a clinically-rated instrument for screening and routine outcome monitoring, offering utility in both clinical practice and research settings for the dimensional assessment of broad psychopathological dimensions. Trial registration German Clinical Trials Register (DRKS) DRKS00016737 ( https://www.drks.de/DRKS00016737 ). Registered 17 September, 2019.