This study described the psychometric properties of a self-report measure of functional impairment related to anxiety and depression in adolescents, the Adolescent Life Interference Scale for Internalizing symptoms (ALIS-I). A clinical sample of 266 adolescents and a community sample of 63 adolescents, aged 11 to 18 years (Mean = 14.7, SD = 1.71) completed the ALIS-I and additional measures assessing internalizing problems. Exploratory factor analyses indicated four distinct but correlated factors of life interference related to personal withdrawal/avoidance, peer problems, problems with study/work, and somatic symptoms. Reliability and retest reliability (8–12 weeks) of the total score were high and psychometric properties of the subscales were acceptable. The ALIS-I effectively discriminated between clinical and community control groups, and expected correlations were shown between ALIS-I subscales and other related symptom measures. The ALIS-I is a promising instrument for the assessment of functional impairment related to internalizing disorders in youth.
