TMJD and Anxiety: Is there a link?

Back in November I saw a meme that stated something like “the psoas muscle is the first muscle to respond in the startle reflex.” I thought that sounded like it deserved a fact checking so I dove down the rabbit hole. I didn’t know much about the startle reflex and was curious. What I really wanted to know was what parts of the musculoskeletal system were activating and in what order.

Probably a tall order, I mean how does a recently un-retired armchair reader of research go about satisfying this query? This Wikipedia article about the startle response [1] was the first stop and the article stated “[t]he fastest reflex recorded in humans happens within the masseter muscle or jaw muscle.” The response occurs in a descending fashion starting with the head, down through the trunk and the knees. It is a protective response and most usually measured by timing the eye-blink. While I am sure the psoas muscle gets activated, it is hardly first and at best is a late middling muscle to respond.

This got me wondering though, I’ve always asked my patients who say “I carry my stress in my neck, shoulders, and jaw” to think about someone who has been startled. What do they look like? Shoulders scrunched up, back of the head tucked in, the body tenses up momentarily. This is like a sudden state of hypervigilance and being anxious or stressed out all the time is kinda like walking around with a low-grade version of that. But is that accurate?

I took a deeper dive and found this article [2] looking at the startle response in people with anxiety disorders. What they wanted to know is whether the startle response is modulated by the autonomic nervous system and/or attentional focus, do emotional states (induced and self reported) influence the magnitude of the response, and whether there is a difference in startle response between someone with GAD and those without. Previous studies have found that baseline startle response is pretty much the same for all people regardless of panic disorder or PTSD diagnoses, but when a negative affect or emotional state is present the reflex becomes stronger or more amplified. This study confirmed what those previous studies found; when attention is focused (inward or outward) and when one perceives themselves to be in a negative emotional state (like, say, feeling anxious) the magnitude of their startle response is higher, more so for people with GAD. So basically, when you drop your vigilance and focus on something, your startle reflex can be much stronger (which draws some connections between people who are hypervigilant and have a desire to never be caught off guard and problems with focus and attention). In addition, if you are already in a negative mood (anxious, depressed, upset etc) your startle response may also be much stronger.

Thinking back to the links between the facial muscles and the startle response I wondered about the relationship between TMJD, stress, and anxiety. This article [3] looked at links between salivary cortisol (stress hormone) and muscle activity in the masticatory (chewing) muscles. They found a correlation between them; with higher salivary cortisol came more severe TMJD presentations. This study [4] also looked at links between stress and the masticatory system finding that “[c]hronic stress may reveal or exacerbate symptoms of masticatory dysfunction.” This systematic review [5] looked at 33 articles examining relationships between anxiety and TMJD, finding that, though the certainty of the evidence is a bit shaky, there does appear to be a consistent link between anxiety and TMJD. There were several others I didn’t have full access to (here [6], here [7], and here [8] [this one is actually a 3-4-1 examining relationships between TMJD and life events, anxiety, and major depressive disorder]) that also indicate there is a link between psychological health and TMJD.

I wonder if the line I intuitively draw between muscle tension, clenching, stress, and anxiety has to do with the physicality of our emotional experiences. Our bodies express our feelings. When we are sad we cry. When we are happy we smile. When we are angry we ball up our fists and our hearts race. And when we are scared (the core emotion of stress and anxiety) we tense up. I think a lot of this is normal expression of the emotional and cognitive parts of the human experience. Our bodies are vehicles of communication; they tell us about what’s what in our world through sensations and our physiology, and they communicate with the world around us through body language (posture, movement, facial expressions, etc). It makes sense that, in the same way repetitive movements can lead to muscular injuries like tendonitis, habitual modes of expression can lead to issues like persistent muscle tension and even pain. Jaw clenching may be a way of trying to release or express pent up nervous energy. One patient recently said to me that clenching his jaw was like a private way he could express his anxiety without people being able to see it (unlike fidgeting or knee bouncing).

If I may wax a bit philosophically, I think the chronicity of these symptoms of tension (chronic to the point of persistent pain in the head, face, jaw, neck, upper back and shoulders) likely has to do with the chronicity of stress exposure in our lives, often to things we may not be able to do anything at all about. We live in a culture that frequently alienates us from not just each other but even from ourselves. Unable to respond to the stressor and create a change, we are stuck with just managing its presence in our lives, bearing the burdens. Even that phrase evokes the image of a body under tension, jaw clenched, resigned to surviving what can sometimes feel unliveable.

Does this mean TMJD, or other muscle tension related problems are all in your head? Absolutely not. No way. In fact, I think it means that what goes on with you psychologically and socially will likely have a presentation or expression in your biology, including your muscular system. And maybe this means massage therapy can be helpful not just for the bodily symptoms, but perhaps also as a bottom-up self care method for the psychological experiences tied to issues like chronic pain and TMJD.

References

1. Startle Response, Wikipedia. Accessed December 11 2023. https://en.m.wikipedia.org/wiki/Startle_response

2. Ray, W. J., Molnar, C., Aikins, D., Yamasaki, A., Newman, M. G., Castonguay, L., & Borkovec, T. D. (2009). Startle response in generalized anxiety disorder. Depression and anxiety, 26(2), 147–154. https://doi.org/10.1002/da.20479

3. Tosato, Juliana & Caria, Paulo & Gomes, Cid & Bérzin, Fausto & Politti, Fabiano & Gonzalez, Tabajara & Biasotto-Gonzalez, Daniela. (2015). Correlation of stress and muscle activity of patients with different degrees of temporomandibular disorder. Journal of Physical Therapy Science. 27. 1227-1231. https://doi.org/10.1589/jpts.27.1227

4. Anna, S., Joanna, K., Teresa, S., Maria, G., & Aneta, W. (2015). The influence of emotional state on the masticatory muscles function in the group of young healthy adults. BioMed research international, 2015, 174013. https://doi.org/10.1155/2015/174013

5. Dos Santos, E. A., Peinado, B. R. R., Frazão, D. R., Né, Y. G. S., Fagundes, N. C. F., Magno, M. B., Maia, L. C., Lima, R. R., & de Souza-Rodrigues, R. D. (2022). Association between temporomandibular disorders and anxiety: A systematic review. Frontiers in psychiatry, 13, 990430. https://doi.org/10.3389/fpsyt.2022.990430

6. Liou, Y. J., Bai, Y. M., Tsai, S. J., Chen, T. J., Chen, M. H., & Lo, W. L. (2023). Bidirectional Associations of Temporomandibular Joint Disorders with Major Depressive and Anxiety Disorders. The journal of evidence-based dental practice, 23(2), 101860. https://doi.org/10.1016/j.jebdp.2023.101860

7. Velly, Ana Miriama,b,c,d,*; Look, John O.a; Carlson, Charlese; Lenton, Patricia A.a; Kang, Wenjunf; Holcroft, Christina A.c; Fricton, James R.a,f. The effect of catastrophizing and depression on chronic pain – a prospective cohort study of temporomandibular muscle and joint pain disorders. Pain 152(10):p 2377-2383, October 2011. | https://doi.org/10.1016/j.pain.2011.07.004

8. Gerke, D. C., Goss, A. N., & Bassett, D. L. (1990). Psychological factors in temporomandibular joint dysfunction: life events. Australian prosthodontic journal, 4, 29–34. https://pubmed.ncbi.nlm.nih.gov/2096892/