Based on the notion that adolescence influences susceptibility to the emergence of emotional disorders and impacts happiness8,9 and because the first signs and symptoms of TMD often appear in childhood and adolescence, the aim of the present study was to investigate associations between temporomandibular joint disorder (TMJ) happiness, and polymorphisms in the COMT (rs165656, rs174675), HTR2A (rs6313, rs4941573), and FKBP5 (rs1360780, rs3800373) genes in adolescents. This evidence concerns the gene COMT and temporomandibular joint disorder.