How negative and positive constructs and comorbid conditions contribute to disability in chronic orofacial pain

BACKGROUND: Temporomandibular disorders (TMD) symptoms develop into chronic pain for some patients, but the reasons for this are unclear. Psychosocial factors and chronic overlapping pain conditions are believed to contribute to the development of pain-related disability. We examined the role of jaw function, negative and positive psychological factors and chronic overlapping pain conditions (COPCs) on pain-related disability whilst controlling for demographic variables. METHODS: We collected demographics, medical and psychosocial history and the Graded Chronic Pain Scale, a measure of pain intensity and pain interference from 400 participants with chronic TMD. Structural equation modelling was used to assess a model of COPCs and the latent variables of psychological unease (pain catastrophizing, somatic symptoms and negative affect), positive valence factors (optimism and positive affect), jaw function (chewing, opening and expression limitation) and pain-related disability (pain intensity and pain interference) whilst controlling for demographic variables. RESULTS: We achieved good fit of a parsimonious model (root-mean-square error of approximation = 0.063 [90% CI] [0.051-0.075]), comparative fit index = 0.942, standard root-mean-square residual = 0.067. Jaw function was the strongest latent variable predictor, followed by psychological unease and COPCs suggesting resources focused on improving joint function, psychosocial support and management of COPCs will improve pain-related disability in TMDs. CONCLUSIONS: These findings not only increase the body of knowledge related to TMD clinical phenotypes but also, have a translational impact in further supporting the potential value of targeting physical therapy such as jaw exercise along with psychological interventions as multidisciplinary nonpharmacological therapeutic solutions.