Alexithymia and pain in temporomandibular disorder

Abstract

Objective

To clarify the relationship of global alexithymia and its facets with pain, assessed prospectively using experience sampling methods (ESMs), in temporomandibular disorder (TMD).

Methods

People with painful TMD (n=49), pain-free somatic controls (24 people with disk displacement), and healthy controls (n=28) completed measures of alexithymia (Toronto Alexithymia Scale-20 [TAS-20]) and depressed mood. Patients with painful TMD used ESM to record jaw pain multiple times daily for a week.

Results

The somatic and the healthy controls were equivalent on alexithymia and were combined. The painful TMD group had higher difficulty in identifying feelings but lower externally oriented thinking (EOT); only the latter effect remained after covarying depressed mood. Among patients with painful TMD, the TAS-20 total and EOT correlated positively with pain severity after controlling for depressed mood.

Conclusion

Findings highlight the complex relationships of alexithymia and its facets to TMD pain. Research should examine alexithymia facets separately and distinguish between methods that compare groups on alexithymia (e.g., pain patients versus controls) and those that correlate alexithymia with pain severity within a group.

Introduction

Chronic pain patients typically have higher alexithymia levels than controls [1], [2], [3], [4], [5], [6]. Correlational studies, however, have had with mixed results, with some studies showing a positive relationship between alexithymia and acute pain during laboratory procedures [7], [8], [9], but other studies reporting limited or no relationships between alexithymia and pain severity [1], [2], [10]. Thus, it remains unclear whether alexithymia is elevated only when pain patients as a group are compared with pain-free controls or whether alexithymia also is associated with the severity of pain among chronic pain patients.

Temporomandibular disorders (TMD) involve the muscles of mastication and the hard and soft tissues of the temporomandibular joint (TMJ) [11], [12]. Primary symptoms of TMD are pain, clicking or grating sounds in the joint, and difficulty opening the mouth wide. Signs of TMD are intermittently experienced by many people, but only 5% to 10% of adults seek treatment for the disorder [13], [14]. Two surveys in Finland found that people reporting orofacial pain reported higher alexithymia than did asymptomatic people [15], [16], but respondents in these studies did not receive evaluations or diagnoses of TMD.

A number of issues remain unclear. First, it is unknown whether alexithymia is elevated among people with formally diagnosed, painful TMD, and whether alexithymia is elevated in those with TMJ dysfunction that lacks pain (e.g., TMD disk displacement). Second, the relationship between alexithymia and pain severity among those with painful TMD needs to be evaluated. Third, research should examine whether the various facets of alexithymia (as measured with the Toronto Alexithymia Scale-20; TAS-20) [17] relate to pain differently. For example, the facets of difficulty identifying feelings (DIF) and difficulty describing feelings (DDF) often predict symptoms, whereas externally oriented thinking (EOT) often does not [18], [19], [20], [21]. Fourth, analyses should test whether alexithymia is related to pain both before and after controlling for negative affect [22], [23]. Finally, previous studies of alexithymia and pain have measured pain with retrospective questionnaires, which have various limitations and usually overestimate the relationship magnitude. Experience sampling methodology (ESM) obviates these limitations by prompting respondents at random times during the day to report their pain as currently experienced, but ESM has not been used in any alexithymia study.

This study examined the relationship between alexithymia and painful TMD using two methods. We first tested the hypothesis that alexithymia is higher among people with diagnosed painful TMD compared with two control groups—people with pain-free TMD and healthy controls. Second, we assessed pain severity using ESM among people with painful TMD and correlated alexithymia with pain severity. In both sets of analyses, we examined global alexithymia and the three facets, and we examined the relationships both before and after controlling for depressed mood to test the unique role of alexithymia.