ANKK1 and Anxiety: To this end, we selected candidate genes that regulate endogenous mechanisms of pain, stress, and anxiety as follows: Dopamine Receptors (DRD2), Ankyrin Repeat and Kinase Domain Containing 1 (ANKK1), Catechol-O-Methyl transferase (COMT), and Serotonin Transporter gene (5-HTT), and to investigate their association with TMD in that population.