Scale development and psychometric properties of internalizing symptoms: The interRAI Child and Youth Mental Health internalizing subscale.

Internalizing difficulties in children and adolescents refer to inner-directed disordered mood and emotions. The purpose of this study was to develop and assess the reliability and validity of the internalizing subscale on the interRAI Child and Youth Mental Health (ChYMH) in assessing broadband internalizing mental health symptoms. Data were collected from clinically-referred children/youths 4 to 18 years of age between 2015 and 2016 (N = 2536). After initial items relevant to internalizing disturbances underwent expert content validation, exploratory first-order and bifactor factor analyses and multidimensional item response theory (MIRT) parameterizations were conducted to test the validity of the measurement model. The internalizing subscale demonstrated strong measurement properties for a three-factor structure (i.e., depression, anxiety, anhedonia) and MIRT analyses showed individual items had acceptable discrimination parameters across the latent continuum. A series of four competing models using confirmatory factor analyses were conducted in a separate sample of 1397 children/youth assessed in 2017 and the bifactor model showed superior fit compared to other models. Finally, concurrent validity of this measure was confirmed based on relationships with other established subscales from criterion measures. The interRAI ChYMH internalizing subscale could be used to provide useful information for triaging and prioritizing referrals for children/youths.