Diagnostic Accuracy of the Child and Adolescent Symptom Inventory (CASI-4R) Substance Use Subscale in Detecting Substance Use Disorders in Youth

Identifying substance use disorders (SUDs) early and accurately improves case formulation and treatment. Previous studies have investigated validity and reliability of the Child and Adolescent Symptom Inventory (CASI) for anxiety, mood, and behavior problems. The present study's aim was to test if the embedded CASI Substance Use (SU) subscale can discriminate adolescents and young adults (AYA) with and without a SUD diagnosis accurately enough to justify clinical application within an evidence-based assessment framework. N = 479 outpatient AYA (age 14-21) and their caregivers completed K-SADS-PLW semistructured diagnostic interviews; caregivers completed the CASI and adolescents completed a parallel version, the Youth (self-report) Inventory (YI). K-SADS-PLW indicated that 33 youth met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for SUDs. Receiver Operating Characteristic (ROC) analyses found that both CASI and YI Substance Use subscale scores significantly identified K-SADS-diagnosed SUDs in AYA: Caregiver area under curve (AUC) = .91, p < .0005; YI(AUC) = .90, p < .0005. There was no significant difference in diagnostic accuracy between informants. Both subscales showed diagnostic and clinical utility in identifying AYA SUDs in outpatient mental health settings. Findings suggest that the CASI-4R subscale could be a helpful screening instrument for AYA SUDs. A case vignette illustrates the clinical application of study findings. Future research should examine rapport as a moderator of reporting accuracy, and replicate use of these measures under varying clinical scenarios. Public Significance Statement Averaging substance use subscale items on the Child and Adolescent Symptom Inventory is a quick way to determine risk of a substance use disorder. Low scores effectively rule out substance concerns in outpatient mental health settings; high scores increase the odds of a substance use disorder diagnosis and warrant further assessment with more specialized methods.