Development and Validation of a Multi-Informant Scale for Assessing Youth Tonic and Phasic Irritability.

Irritability is a common mental health issue in children and adolescents which strongly predicts later psychopathology and impairment. It can manifest in tonic (persistent angry mood) and phasic (short temper outbursts) forms, but research on this distinction is limited due to the lack of validated measures. We developed and evaluated the first multi-informant measure of tonic/phasic irritability for school-age children and adolescents. Data was collected from four samples including three community samples (a total of 1208 parents of 6-17-year-old children and 876 unrelated 13-17-year-old youth) and a small clinical sample (92 parents and their 10-17-year-old children). The Tonic and Phasic Irritability Scale (TAPIS) consists of 8 items measuring tonic, and 11 items measuring phasic, irritability. It demonstrated strong psychometric properties, including structural validity, test-retest stability, and construct validity. Consistent with the literature, tonic irritability was associated with internalizing problems (i.e., anxiety, depression), while phasic irritability was related to externalizing behaviors (e.g., aggression, conduct problems, substance use). The TAPIS exhibited measurement invariance across gender, age, informant, and history of mental health treatment. These findings provide preliminary support for the TAPIS' reliability and validity and demonstrate its promise helping to elucidate differences in the development and treatment of tonic and phasic irritability.