Several studies of TMJD suggest that patients exhibit a state of CNS hypersensitivity similar to that reported in fibromyalgia (Maixner et al 1995, Maixner et al 1998, Sarlani and Greenspan 2003, Sarlani et al 2004) that contributes to the predicted widespread characteristics of the pain. Genetic factors that impact increased pain sensitivity, psychological traits and sex differences, and often coupled with environmental stress, may result in a phenotype that is vulnerable to musculoskeletal disease and susceptible to selective pharmacological treatment.