Summary and Next Steps

Altered Facial Feedback May Be Missing Link in Mental Health Disorders

Exaggerated facial feedback from altered facial muscles and connective tissue due to TMD may be a “missing link” in understanding the development of clinical anxiety and depression—connecting psychological challenges to abnormal and enduring physiological responses. Mental health challenges begin when stressful life events initiate negative or even catastrophic interpretations (Fenn & Byrne, 2013). Negative thoughts also trigger stressful facial expressions. Multiple studies show that facial expressions initiate or intensify emotions (Strack et al., 1988; Soussignan, 2002; Larsen et al., 2003; Lewis, 2012). Even without emotional stimulus, sad and angry facial expressions activate the amygdala—where negative emotions are processed (Hennenlotter et al., 2008; LeDoux, 2000). The strength of facial expressions seems to make a difference in emotional outcomes, as it correlates with cortisol levels and cardiovascular responses (Lerner, 2007; Kraft & Pressman, 2012; Pressman et al., 2021) as well as the magnitude of amygdala activation (Heller et al., 2014). With the face so involved in emotional responses, it is logical that facial injuries may alter the magnitude of those responses.

TMD May Amplify Facial Feedback Responses

Researchers indicate that TMD facial injuries could alter normal autonomic responses through hyperactivity in the temporalis and masseter muscles and joints (Auerbach et al., 2001), which would then exaggerate facial feedback and amplify emotional responses. Stress-induced TMD alterations could occur during prolonged or intense psychological distress (Namvar, 2021), such as during university studies or during battle. They might also occur from trauma, childhood neglect, or abuse—known risk factors for depression (Lippard & Nemeroff, 2020). Many people with TMD and depression may likely go undiagnosed, as randomly selected study participants were diagnosed with both conditions (Restrepo et al., 2021; Al-Khotani et al., 2021).

TMD and Mental Health Disorders May Be Bidirectional

TMD and mental health disorders are frequently comorbid (seen together) and likely bidirectional. The adverse effects of either could initiate and maintain the other, making these disorders cyclical. Understanding the connection between TMD, depression, and anxiety may help in healing all these disorders. The early success of BTX treatment for depression suggests that facial feedback contributes to depression—and immobilizing facial muscles may assist in recovery. Psychological treatments have proven effective in treating TMD (Turk et al., 1996; Auerbach, 2001; Li & Leung, 2021). Diagnosing and treating TMD in depressed patients may also speed recovery from depression. However, no studies yet to date have yet confirmed this assumption. Future research may help resolve these theories.

Next Steps—Facial Feedback and Mental Health

Additional research is currently being done at Cardiff University in Cardiff, Wales, to measure the impact of TMD on facial feedback responses. Future research could assess patients in mental health hospitals for TMD and determine if TMD treatments are beneficial to patients with mental health disorders.

Last updated October 9, 2023

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References

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