RESUMO
The Kessler psychological distress scale is a useful tool for identifying possible psychological problems and has been widely used in research and health services. Unfortunately, its application in various populations has not always been psychometrically supported. For this reason, the present study investigated the psychometric properties of its Spanish version in adolescents, verifying its factorial structure, measurement invariance by gender, internal consistency and the discrimination and difficulty parameters of its items according to the Item Response Theory (IRT). A sample of 5132 Ecuadorian adolescents was evaluated. The sample is equally distributed between male and female participants (50%) and basic and higher education (51% the former). All participants were between 11 and 20 years old. The results show that a 9-item version with correlated intercepts presents the best fit. In addition, it is invariant by gender at a strict level and has adequate internal consistency. IRT analyses indicated that all the items, except for item eight, present adequate discrimination and difficulty. Based on these results, we conclude that the 9-item version of the Psychological Distress Scale is the most appropriate for this population.