The Avoidance and Fusion Questionnaire for Youth (AFQ-Y8) was developed to measure psychological inflexibility. Although the questionnaire is a well-known tool in clinical practice, its psychometric properties have not been widely investigated in the target population of children and adolescents. The purpose of this study was to investigate the factor structure and validity of the AFQ-Y8 (N = 1,572, mean age 15.39 years, girls 51%) on a Hungarian sample. We also tested the invariance of the measurement model across two age groups (11-14 and 15-20 years old). Results confirmed the single-factor structure of the AFQ-Y8. Psychological inflexibility was also found to be positively related to emotional instability, externalizing, and internalizing problems. Furthermore, psychological inflexibility explained the variance of life satisfaction when personality dimensions, emotional, and behavioral problems were accounted for. Measurement invariance across age groups was partially supported. These results suggest that the AFQ-Y8 is a reliable and valid instrument for assessing psychological inflexibility in children and adolescents.
Keywords: AFQ-Y8; age invariance; cognitive fusion; confirmatory factor analysis; convergent validity; experiential avoidance; psychological inflexibility.