Development and Psychometric Evaluation of the Tehran Adolescent Aggression Scale: A Mixed-Methods Study

Background: Adolescent aggression is a significant mental health concern that affects the quality of life, particularly in Tehran. The absence of a standardized and culturally adapted instrument for assessing aggression among Tehran’s adolescents prompted the development of the Tehran Adolescent Aggression Scale (TAAS). Objective: This study aim to provide a foundation for forecasting future trends, alleviating psychological and social issues, and guiding focused mental health strategies. Thus, TAAS can significantly contribute to raising public awareness, upgrading educational standards, and strengthening social unity, thus offering essential data for researchers and mental health professionals. Methods: This developmental mixed-methods study was conducted in Tehran, Iran, from 2022 to 2023. In the qualitative phase, 22 adolescents aged 14 to 18 were purposefully sampled from diverse districts of Tehran to ensure cultural and social representation, achieving data saturation after 22 interviews. An in-depth content analysis of these interviews led to the development of a 30-item TAAS. In the quantitative phase, 1,051 adolescents were selected using cluster sampling from various schools across Tehran. The TAAS was validated through both qualitative and quantitative face validity, content validity [using the Content Validity Index (CVI) and content validity ratio (CVR)], and concurrent validity [via simultaneous administration with the Buss-Perry Aggression Questionnaire (BPAQ)], as well as exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Reliability was assessed using Cronbach’s alpha and split-half reliability, with data analyzed using SPSS and Lisrel. Results: The newly developed TAAS demonstrated strong face validity both qualitatively and quantitatively. Content validity was robust, with CVR values ranging from 0.81 to 0.89 and CVI values between 0.86 and 0.92, surpassing minimum standards. Concurrent validity results confirmed the instrument's accuracy (P = 0.001, R = 0.82). The EFA revealed an eight-factor structure that explained 67.03% of the variance, and this structure was further validated through CFA. Overall, the TAAS exhibited excellent reliability, with a Cronbach’s alpha of 0.95 and subscale alphas exceeding 0.77. Conclusions: The TAAS is a reliable and valid tool for assessing aggression in Tehran’s adolescent population, offering a significant contribution to clinical practice and research in adolescent mental health.