The interRAI Child and Youth Mental Health (ChYMH) is a standardized assessment instrument utilized in over 60 mental health agencies that promotes seamless transition across public healthcare sectors. The purpose of this study was to develop and assess the reliability and validity of the externalizing subscale on the interRAI Child and Youth Mental Health (ChYMH). Part one invited a panel of experts (i.e. doctoral-level clinical psychologists) to assess content validity of the items relevant to externalizing behaviors. Items that experts deemed representative of externalizing symptoms underwent unrestricted factor analyses in a sample of children/youths 4 to 18 years of age (N = 3,464) collected across 39 mental health agencies. The final externalizing subscale showed strong content representativeness, high internal consistency, and good structural validity for a two-dimensional model of reactive and proactive externalizing behavior. In part two, Bayesian correlations demonstrated that the interRAI ChYMH externalizing subscale showed strong associations with externalizing subscales, anger, and disruptive behavior measures from various assessment instruments (i.e. Beck Youth Inventories, Social Skills Improvement System, Child and Adolescent Functional Assessment Scale, Child Behavior Checklist, Brief Child and Family Phone Interview). Overall, the externalizing subscale demonstrated strong measurement properties for the assessment of behavioral disturbances.
Keywords: child; externalizing; interRAI; mental health; scale.