Psychological factors related to the prevalence of temporomandibular joint sounds.

This study focuses on the association between psychological factors and TMJ sounds, and the most suitable research design to establish this relation. A traditional research design is simulated to demonstrate how self-report may bias findings. A refined design is presented to obtain unbiased estimates of the role of psychological variables. In the 'naïve' design the importance of psychological variables was overestimated and the role of physiological variables was underestimated. It was concluded that future studies in the aetiology of TMJ clicking should abandon the use of self-report as a proxy for objective findings. With the refined design it was found that psychological factors play only a minor role in the prevalence of TMJ sounds. Findings do not support speculation about mechanisms that relate psychological factors to the presence of TMJ sounds.