Decision-making capacity in children and adolescents in healthcare requires thorough assessment: the minor's maturity, understanding of the decision, risk of the situation and contextual factors needs to be explored. The intention was to design and validate a test-the Maturtest-to assess the maturity of minors in decision-making processes in healthcare. A reasoning test on moral conflicts for adolescents was designed to infer the degree of maturity of minors applied to decision-making regarding their own health. The test was completed by a sample of 441 adolescents aged from twelve to sixteen, with a corresponding analysis of their psychometric skills to measure feasibility, viability, reliability, validity, and sensitivity to change. Psychometric test results showed viability, reliability, validity, and sensitivity to change. High correlation (correlation index = 0.74) between the test score and the reference method were notable. A high stability was obtained with an intraclass correlation coefficient (r = 0.77). The average response time of the test was twenty-three minutes. This test measures the moral maturity of adolescents. It is presented as an objective, useful, valid, reliable tool, easy to fill out, edit and apply in a healthcare context. It helps to assess the maturity of minors faced with a decision.
Keywords: Adolescent; Capacity; Ethics; Health decision-making; Mature minor.