&in, 44 (1991) 29-34 0 1991 Elsevier Science Publishers ADONIS 0304395991000527
29 B.V. (Biomedical
Division)
0304-3959/91/$03.50
PAIN 01703
Psychological distress and diagnostic subgroups of temporomandibular disorder patients Charles P. McCreary,
Glenn T. Clark, Robert
Denial Research Institute, (Received
17 January
UCLA Schools 1990, revision
L. Merril, Virginia Flack and Mark E. Oakley
of Medicineand Dentistry, Los Angeles, CA (U.S.A.) received 29 May 1990, accepted
11 June 1990)
This study examined the nature and extent of psychological differences among diagnostic subgroups of temporomandibular SummarY dtsorder (TMD) patients. Three subgroups were identified and labeled as: (1) primary myalgia, (2) primary temporomandibular joint (TMJ) problems, or (3) combination myalgia and TMJ problems. Patients’ (n = 112) levels of pain and distress were measured using a VAS pain scale, the McGiB Pain Questionnaire, the Beck Depression Inventory, the State-Trait Anxiety Scale and the MMPI. Patients with primary myalgia had the highest scores on the pain and distress measures while patients in the combination group scored between the myalgia and TMJ problem subgroups. When differences in pain levels were controlled, the differences among groups on measures of anxiety and depression were attenuated while the differences on measures of somatic overconcern remained significant. Discriminant function analysis using psychological variables to predict diagnostic grouping produced correct identification of 74% of the structural patients and 46% of the myalgia patients. Implications for different etiological factors among the 3 groups are discussed. Key words:
Diagnostic
subgroups;
Temporomandibular
disorder;
Pain; Distress
There is controversy about the importance of psychological factors in the etiology and progression of temporomandibular (TM) disorders. Clarification of this issue is impeded by the lack of reliable and validated classification procedures for separating TM disorders into diagnostic subgroups and the existence of discrepant etiological models for these conditions. The 2 prevalent etiological models used in relation to TM disorders where external trauma was not the cause either emphasized or minimized the importance of stress as a causative agent. The first model, the structural disharmony or biomechanical model, maintains that certain dental-occlusal abnormalities lead to abnormal jaw muscle and joint function with eventual pain. Psychological distress is regarded as a consequence of the discomfort and frustrations presented by the disorder. This model gained prominence in the early 1930s [6] and subsequently the use of occlusal-biomechanical treatment methods predominated in the 194Os, 1950s and 1960s [3]. During this time structural conditions
Correspondence to: Dr. Charles McCreary, Department of Psychiatry and Biobehavioral Sciences, 760 Westwood Plaza, Los Angeles, CA 90024-1759, U.S.A.
such as occlusal interferences were considered as potential causes of TM disorder [4,5]. More recently this model re-emerged with the new focus on developmental abnormal or acquired occlusions producing pathological TM joint function in terms of internal derangements and pain. In the 1960s and 1970s another model became predominant. This model, the psychophysiological model, proposed that, except for obvious degenerative arthritic conditions and problems induced by external trauma, temporomandibular disorders were not due to occlusal abnormalities but had stress as a primary cause. Certain life stressors led to dysfunctional oral habits (clenching, grinding and related muscle tension) that created chronic muscle strain and facial pain. The constellation of symptoms involving pain, limited opening of the jaw and joint noises were called the myofascial pain dysfunction (MPD) syndrome [13,14]. Recent perspectives on temporomandibular disorders have proposed that they are multifactorial problems with structural (occlusion), functional (bruxism), external trauma, arthritic deterioration and psychological (anxiety, tension) factors as interrelated causes [7,18,20]. Furthermore, prompted by new anatomic and radiographic studies, Clark [3] suggested that TMD patients have many clearly different diagnostic problems including internal derangements, osteoarthritis and myoge-
nous disorders. These newer perspectives suggest that it is important to make a careful diagnostic evaluation of the multiple problems and symptoms of patients in order to appropriately select proper treatment approaches. There is some evidence that different treatments are helpful for patients with different types of TM disorder [2.3,10,11,17,19]. It seems that clarification of the involvement of psychological factors in different kinds of TM disorder patients is important; however, previous research on psychological differences between subgroups of TM disorder patients have not produced consistent results. Eversole, Stone, Matheson and Kaplan [9] compared 2 subgroups of TM disorder patients (a myogenic facial pain group and a TMJ internal derangement group) with a group of patients with atypical facial pain. Patients with myogenic facial pain scored higher on several MMPI scales, reflecting more distress, than did patients with internal derangements. On the other hand, Marbach and Lund [15] studied 3 subgroups of facial pain patients: myofascial pain dysfunction syndrome (MPD), arthritis of the temporomandibular joints and trigeminal neuralgia. Normal comparison groups were also studied. There were no differences in levels of distress between the myofascial pain dysfunction patients and those patients with degenerative arthritis. Both groups showed relatively normal levels of depression, measured with the depression scale of the Institute of Personality and Ability Testing questionnaire and average Spielberger State-Trait Anxiety Inventory scores. However, the MPD patients scored higher on a visual analog pain intensity scale than the TMJ arthritis patients. Dworkin, LeResche, Von Korff, Truelove and Sommers [8] used the Eversole et al. [9] diagnostic system as well as their own criteria to categorize patients seen in the clinic or a randomly sampled group of community cases with facial pain problems. Patients were fairly equally divided into those with myofascial pain dysfunction, internal derangements, and degenerative joint disease. The Eversole et al. [9] diagnostic categories were not related to levels of stress, anxiety, depression or somatic concern as measured by the Symptom Check List-90 (SCL-90). However, their own system found,that the diagnosis of MPD was associated with higher levels of anxiety, depression and somatization. The purpose of this article was to explore how diagnostic distinctions were related to the nature and extent of psychological factors in patients with TM disorders. Specifically, the study examined whether patients with a primarily myogenous disorder showed greater psychological distress in comparison to patients with internal derangements or other evidence of a primary articular disorder (i.e., osteoarthritis). Differences in pain levels among the subgroups were considered when examining psychological differences. This
study also explored the strength of the relationship between diagnostic categories and psychological factors by examining the accuracy of identifying diagnostic categories using the psychological variables as predictors.
Method The patients in the study were 112 consecutive patients seen at the UCLA TMJ and Facial Pain clinic, a university-based specialty clinic for TMJ and orofacial problems. The average age of patients was 39 years and there were no age differences among the diagnostic groups (described below). The overall sample was 86% female. Although there was a trend for fewer women in the myalgia group (77%), versus 93% in the mixed and 84% in the structural groups, there was not a significant difference in sex composition of the 3 diagnostic groups. The average number of months since the start of their TMD was 68 and there were no differences in chronicity among the diagnostic groups. Subjects were not included if they exhibited symptoms or history of a primary neurogenous disorder (trigeminal or postherpetic neuralgia); dental, periodontal or other orofacial infection; or an episodic vascular headache (e.g., cluster or migraine). The patients underwent a complete medical-dental history, clinical examination and were asked to fill out a number of psychological tests prior to their treatment at the clinic. The clinical examination consisted of a careful assessment of the range and quality of jaw movement difficulties, palpation of the muscles of mastication and TM joints and an evaluation of the occlusion. If clinical findings and symptom history indicated the need for a radiographic evaluation, this was also done. All radiographs were axially corrected sagittal tomograms taken in the closed and fully open mouth position. Based upon the above history and examination data, patients were grouped into 3 categories for this study. The first category consisted of patients with primary myalgia. Patients in this category showed substantial masticatory muscle pain symptoms on palpation but did not show joint pain on palpation, cIicking, crepitus or restriction of the normal condylar movement on mouth opening. More specifically, patients in this group reported: (1) moderate to severe tenderness upon palpation (3-5 lbs of pressure) in at least one masseter or temporalis muscle; (2) decreased pain-free jaw movement; and (3) full condyle translation and normal mouth opening was present with passive stretching of the jaw. Pain symptoms typically were described as dull, aching sensations which were continuous and of variable intensity. Characteristically, pain in the morning was worse
31
on awakening and frequently increased in the late afternoon and under conditions of increased stress. The second category of patients was those with a primary TM joint problem. These problems presented clinically as internal derangements or as osteoarthritis. Although these patients often showed evidence of mild to moderate myalgia, it was much less severe than the joint symptoms. The patients with internal derangement presented with primary symptoms of repeated, frequent clicking or popping of the temporomandibular joints on movement. The remaining patients in this group exhibited either TMJ osteoarthritis or internal derangement in the locking phase. The latter patients presented with primary symptoms of limited mouth opening (less than 40 mm interincisally including overbite even after passive stretching). The osteoarthritis patients presented with primary symptoms of TM joint region pain on palpation and movement and exhibited radiographically evident remodeling, flattening and/or spurring of the TM joint. These patients typically showed multiple joint noises or crepitus on movement. A third category of patients showed combined symptoms of both significant myalgia as well as evidence of a TM joint problem as defined above. For these patients the symptoms of myalgia were equal to or more severe than the joint symptoms. Measures A visual analogue scale (VAS) was used to assess the patients’ rating of their current pain level with anchor points at the left- (no pain) and right-hand (most intense pain imaginable) ends of a 100 mm horizontal line. Also, the McGill Pain Questionnaire (MPQ) was used to assess qualitative aspects of the patients’ pain. Patients described their pain by selecting an adjective descriptor from 20 categories and 3 scores were ob-
tained by summing the scale values for the sensory, affective and evaluative categories [ 16 1. Three self-report psychological tests were used to assess pretreatment levels of distress in these patients. These instruments were the Beck Depression Inventory (BDI), The Spielberger State-Trait Anxiety Inventory (STAI) and the Minnesota Multiphasic Personality Inventory (MMPI). The BDI is a 21 item self-rating measure of depression [l]. The State-Trait Anxiety Scale contains 2 subtests of 20 items each, measuring either state or trait anxiety [22]. The MMPI is a 566 item true-false inventory which has many different scales assessing a variety of psychological problems. The MMPI is interpreted by examining scores on the validity scales (L, F and K) which assess the person’s approach to taking the test (i.e., careless or -random responding, faking bad, minimizing faults). The interpretation of psychological difficulties is made by examining scores on the clinical scales which include: hypochondriasis (Hs), which measures concern about bodily functioning; depression (D), which assesses feelings of depression, helplessness, hopelessness; hysteria (Hy), which assesses somatic concerns and denial of emotional or interpersonal problems; and psychasthenia (Pt), which measures ruminations, worry and anxiety. Other clinical scales assess impulsivity and low frustration tolerance (Pd), suspiciousness and distrust (Pa), alienation and confusion (SC) and high energy level and distractability (Ma).
Results Table I presents the psychological scores on the Beck Depression Scale, the Spielberger State/Trait Anxiety Scales and the MMPI scores of the 3 diagnostic groups.
TABLE I BECK DEPRESSION, STATE/TRAIT ANXIETY, ANCE FOR THE DIAGNOSTIC GROUPS Myalgia
(N = 27) Beck
11.6 (1.56)
State anxiety
70.8 (5.70)
Trait anxiety
72.7 (6.24) 72.0 (2.68) 66.5 (2.47) 72.4 (2.14) 63.3 (2.14)
MMPI Hs MMPI D MMPI Hy MMPI Pt
AND MMPI MEAN SCORES, (STANDARD
Combined (N = 37)
TM joint (N = 42)
10.8 (1.33) 58.3 (4.96) 60.7 (5.28) 64.6 (2.13) 61.9 (1.97) 67.6 (1.71) 57.8 (1.70)
6.0 (1.25) 51.3 (4.65) 54.4 (4.94)
ERRORS),
F
AND ANALYSIS
P
5.14
0.01
3.51
0.05
2.67
0.07
56.5 (2.03)
11.02
0.001
56.5 (1.87)
5.46
0.01
59.3 (1.61)
13.14
0.001
55.9 (1.62)
3.85
0.02
OF VARI-
TABLE
II
PAIN SCORE
MEANS.
(STANDARD
ERRORS)
AND ANALYSIS
MPQ affective MPQ evaluative Pain VAS
,
TM joint (N = 47)
F
P
12.0 (1.87) 6.4 (1.15) 2.0 (0.32) 50.6 (5.05)
13.5 (1.57) 3.0 (0.97) 2.2 (0.27) 48.0 (4.33)
7.2 (1.49) 2.4
4.64
0.01
4.09
0.02
1.59
0.21
6.66
0.01
MMPI Scores of Diagnostic Groups
I
GROUPS
Combined (N = 36)
Fig. 1 presents a graph of the MMPI clinical scale scores of the 3 diagnostic groups. There were statistically significant differences between the mean scores of the diagnostic groups on several of the distress measures based on a standard one-way ANOVA. In general, patients with primary myalgia scored higher on these scales than the other 2 groups. Patients with a combined diagnosis consistently showed scores in between those of the myalgia and TM joint subgroups. Table II presents the mean pain scale scores of the various diagnostic groups. There were statistically significant differences between the diagnostic categories on the McGill Pain Questionnaire sensory and affective scores as well as on a visual analog pain intensity scale based on one-way ANOVA. Patients with myalgia scored on average higher on these measures of pain than patients with TM joint problems. Patients with a combined diagnosis consistently had average scores between the myalgia and the TMJ problem patients with the exception of the MPQ evaluative score. In order to assess whether pain levels accounted for the differences between the subgroups on the various distress measures, analysis of covariance was performed with the pain intensity score as the covariate. Two of the scores on the psychological scales remained statisti-
300
FOR THE DIAGNOSTIC
(N = 26)
Myalgia
MPQ sensory
OF VARIANCE
(0.90) 1.6 (0.25) 30.2 (4.04)
tally
significant
(Hs:
F = 5.4, P < 0.01;Hy: F = 7.2,
P < 0.01). However, Pearson correlations between pain scores and the various psychological variables were not consistent across the 3 diagnostic subgroups (see Table III). In the myalgia patients, pain intensity was not correlated with depression and anxiety scores while it was related to the MMPI Hs and Hy scales. Pain was consistently related to the psychological scores in the TM joint problem subgroup. In the combined diagnosis group there were high correlations between pain and depression scores. In order to account for these divergent patterns of correlations among the diagnostic groups, additional covariates were added to the analyses of covariance. The additional covariates, interactions between the pain and the diagnostic group variates, allow for non-parallel lines for the 3 diagnostic groups in the analysis of covariance model. The difference between the groups on the Hy scale (F = 5.32, P < 0.01) remained significant. Discriminate analysis was performed to assess the nature and extent of the relationship between psychological factors and differences among the diagnostic groups. Linear discriminate functions were used to combine the psychological variables in order to predict diagnostic group membership. The 4 MMPI scales (Hs, D, Hy and Pt) that significantly differentiated the groups on a univariate basis were used as the predictors. Sev-
90 I
TABLE
III
CORRELATIONS OF PAIN VAS WITH BECK DEPRESSION, STATE/TRAIT ANXIETY, AND MMPI Hs, D, Hy AND Pt SCORES AMONG THE THREE DIAGNOSTIC SUBGROUPS
4c
!
0
0
o-o
Combined
0
My0kp 0
TMJ
JO_-,
Fjs
D
Hy
Pd
Pa
Pt
SC
Ma
Fig. 1. MMPI clinical scale scores of the 3 diagnostic groups. There were statistically significant differences between the mean scores of the diagnostic groups on several of the distress measures based on a standard one-way ANOVA.
Beck State anxiety Trait anxiety MMPI Hs MMPI D MMPI Hy MMPI Pt
Myalgia
Combined
TM joint
0.09 - 0.08 -0.16 0.49 0.07 0.50 - 0.06
0.52 - 0.04 0.04 0.31 0.42 0.07 0.19
0.30 0.25 0.25 0.48 0.18 0.45 0.39
33
enty-four percent of the patients with a structural diagnosis were correctly identified using their psychological scores. On the other ‘hand, dnly 46% of the myalgia patients were correctly categorized based upon psychological scores. In general, 58% of all patients were correctly assigned to their actual diagnostic group. Thirteen percent of patients were incorrectly identified as either myalgia patients or TM joint patients when their actual diagnosis was TMJ problem or myalgia. The other incorrect predictions (29%) were misclassified as combined versus one of the other 2 diagnostic categories.
Discussion
The results of this study are consistent with those found by Eversole et al. [9] and Dworkin et al. [8] (using their own diagnostic system) who reported more distress m patients with MPD diagnoses versus those with internal derangements. Our findings are also consistent with the Marbach and Lund [15] report of higher pain levels in MPD versus TMJ arthritis patients; however, the present results are inconsistent with their finding of similar levels of depression and anxiety in MPD versus TMJ arthritis patients. The absence of differences in the Marbach and Lund study could be due to inclusion of some patients with structural difficulties in their MPD group. The statistically significant psychological differences among the various diagnostic groups were not strong enough for clinical use in accurately categorizing patients; nevertheless, the differences appeared to have etiological implications. The pattern of scores on pain and distress measures in myalgia patients is consistent with a psychophysiological model of disorder for them. The myalgia group contained large numbers of patients with high levels of distress and pain. However, higher degrees of anxiety and depression were not associated with higher pain levels. Furthermore, these patients showed higher scores on measures of concern about bodily functioning and preoccupation with illness that were not accounted for by differences in pain levels. When myalgia patients are in pain and are preoccupied with worries about physical functioning and fearful about something going wrong with their body, they seem to be avoiding dealing with distressing aspects of their life. This suppression of emotional difficulties may contribute to excess muscle tension and may facilitate dysfunctional oral habits like clenching and bruxing. Since these patients have high levels of pain and distress, they seem to need treatments designed to help them acknowledge stressful life problems and to learn methods to improve their ability to cope with their pain and stress problems. Patients with primary TM joint problems showed
low levels of psychological difficulties consistently across various measures used in this study as well as low to moderate correlations between psychological scores and pain levels. As a group these patients do not show much evidence of psychological difficulties; however, when they are in pain they experience increasing distress. Their distress appears to be a response to the difficulties in coping with the pain precipitated by structural pathology. This process is consistent with a biomechanical model in which structural pathology leads to discomfort and functional difficulties and a distressful emotional reaction. These patients may need stress management yet clearly the first choice in treatment should be therapies directed to their structural problem (i.e., bite appliances, physical therapy, etc.). Patients with a combined diagnosis present more difficulties in making judgments about psychological etiology. Their relatively high Beck Depression scores and their correlations between pain and depression suggest that they are reacting to their pain problems with some depression. They may benefit from combinations of stress management and somatic treatments. It is interesting to compare the above findings with similar studies of headache patients. Kudrow and Sutkus [12] compared MMPI scores of 3 categories of headache patients: migraine, mixed and muscle contraction. They found higher scores on the neurotic triad (Hs, D and Hy) in the muscle contraction patients. The authors speculated that differences in the impact of the pain problem in the person’s life might account for the higher MMPI scores of the muscle contraction patients. In a similar manner, perhaps patients with myalgia are experiencing more stressful life circumstances and more negative illness impact. Research is needed to compare the various diagnostic subgroups in terms of life stress and illness impact.
Acknowledgement
Preparation of this article was supported by Grant DE07618 from the National Institute of Dental Research.
References Beck, A., Depression: Clinical, Experimental and Theoretical Aspects, Harper and Row, New York, 1967. Benson, B.J. and Keith, D.A., Patient response to surgical and nonsurgical treatment for internal derangement of the temporomandibular joint, J. Oral Maxillofac. Surg., 43 (1985) 770-777. Clark, G.T., Diagnosis and treatment of painful temporomandibular disorders, Dent. Clin. North Am., 31 (1987) 645-674. Clark, G.T. and Adler, R., A critical evaluation of occlusal therapy: occlusal adjustment procedures, J. Am. Dent. Assoc., 110 (1985) 743-750.
Clark. G.T.. Solberg, W.K.. Monteiro, A., Temporomandibular disorders: new challenges in clinical management, research and teaching. In: G.T. Clark and W. Solberg (I%.), Perspectives in Temporomandibular Disorders, Quintessence Books. Chicago. IL, 198X. Costen, J.B., Syndrome of ear and sinus symptoms dependent upon disturbed function of the temporomandibular joint. Ann. Otol. Rhinol. Laryngol., 43 (1934) I-15. Dworkin. S.F. and Burgess, J.A.. Orofacial pain of psychogenic origin: current concepts and classification. J. Am.. Dent. Assoc., 115 (1987) 565-571. Dworkin. S.F., LeResche, L., Von Korff, M., Truelove, E. and Sommers, E., Comparing two classification schemes for differences in psychological status, J. Dent. Res.. 68 (1989) 1018 (Abstr.). Eversole, L.R.. Stone, C.E., Matheson, D. and Kaplan, H., Psychometric profiles and facial pain. Oral Surg. Oral Med. Oral Pathol., 60 (1985) 2699274. IO Fricton, J.R., Hathaway, K.M. and Bromaghim, C.. Interdisciplinary management of patients with TMJ and craniofacial pain: characteristics and outcome, J. Craniofac. Dis. Fat. Oral Pain, 1 (1987) 1155122. 11 Gale, E.N., Biofeedback treatment for TMJ pain. In: B.D. Ingersoll and W.R. McCutcheon (Eds.), Clinical Research in Behavioral Dentistry. West Virginia University Foundation. Morgantown, 1979, pp. 83-94. 12 Kudrow, L. and Sutkus, B.J., MMPI patterns specificity in primary headache disorders. Headache, 19 (1979) 18-24.
13 Laskin, D.M., Etiology of the pain-dysfunction syndrome. J. Am. Dent. Assoc., 79 (1969) 147. 14 Malow, R.M., Olson, R.E. and Greene, C.S., Myofascial pain dysfunction syndrome: a psychophysiological disorder. In: Golden, C. et al. (Eds.), Applied Technique in Behavioral Medicine. Grune and Stratton, New York. 1981. 15 Marbach. J.J. and Lund, P., Depression, anhedonia and anxiety in temporomandibular joint and other facial pain syndromes, Pain, 11 (1981) 73-84. 16 Melzack. R.. The McGill Pain Questionnaire: maJor properties and scoring methods, Pain, 1 (1975) 279-299. 17 Moss. R.A., Garrett, J. and Choido. J.F.. Temporomandibular Joint dysfunction and myofascial pain dysfunction syndromes: parameters. etiology and treatment, Psychol. Bull.. 92 (1982) 331l 346. 18 Rugh. J.D., Psychological components of pain. Dent. Clin. North Am.. 31 (1987) 579-594. 19 Scott, D.S. and Gregg, J.M., Myofascial pain of the temporomandibular Joint: a review of the behavioral-relaxation therapies, Pain. 9 (1980) 231-242. 20 Solberg, D.K.. Temporomandibular disorders: background and the clinical problems, Br. Dent. J., 160 (1986) 157-161. 21 Solberg, W.K., Flint, R.T. and Brantner, J.P., Temporomandibular Joint pain and dysfunction: a clinical study of emotional and occlusal components, J. Prosthet. Dent., 28 (1972) 412-422. 22 Spielberger, C.. Gorsuch, R. and Tushene, R., State-Trait Anxiety Inventory Manual. Consulting Psychology Press, Palo Alto, 1970.
29 B.V. (Biomedical
Division)
0304-3959/91/$03.50
PAIN 01703
Psychological distress and diagnostic subgroups of temporomandibular disorder patients Charles P. McCreary,
Glenn T. Clark, Robert
Denial Research Institute, (Received
17 January
UCLA Schools 1990, revision
L. Merril, Virginia Flack and Mark E. Oakley
of Medicineand Dentistry, Los Angeles, CA (U.S.A.) received 29 May 1990, accepted
11 June 1990)
This study examined the nature and extent of psychological differences among diagnostic subgroups of temporomandibular SummarY dtsorder (TMD) patients. Three subgroups were identified and labeled as: (1) primary myalgia, (2) primary temporomandibular joint (TMJ) problems, or (3) combination myalgia and TMJ problems. Patients’ (n = 112) levels of pain and distress were measured using a VAS pain scale, the McGiB Pain Questionnaire, the Beck Depression Inventory, the State-Trait Anxiety Scale and the MMPI. Patients with primary myalgia had the highest scores on the pain and distress measures while patients in the combination group scored between the myalgia and TMJ problem subgroups. When differences in pain levels were controlled, the differences among groups on measures of anxiety and depression were attenuated while the differences on measures of somatic overconcern remained significant. Discriminant function analysis using psychological variables to predict diagnostic grouping produced correct identification of 74% of the structural patients and 46% of the myalgia patients. Implications for different etiological factors among the 3 groups are discussed. Key words:
Diagnostic
subgroups;
Temporomandibular
disorder;
Pain; Distress
There is controversy about the importance of psychological factors in the etiology and progression of temporomandibular (TM) disorders. Clarification of this issue is impeded by the lack of reliable and validated classification procedures for separating TM disorders into diagnostic subgroups and the existence of discrepant etiological models for these conditions. The 2 prevalent etiological models used in relation to TM disorders where external trauma was not the cause either emphasized or minimized the importance of stress as a causative agent. The first model, the structural disharmony or biomechanical model, maintains that certain dental-occlusal abnormalities lead to abnormal jaw muscle and joint function with eventual pain. Psychological distress is regarded as a consequence of the discomfort and frustrations presented by the disorder. This model gained prominence in the early 1930s [6] and subsequently the use of occlusal-biomechanical treatment methods predominated in the 194Os, 1950s and 1960s [3]. During this time structural conditions
Correspondence to: Dr. Charles McCreary, Department of Psychiatry and Biobehavioral Sciences, 760 Westwood Plaza, Los Angeles, CA 90024-1759, U.S.A.
such as occlusal interferences were considered as potential causes of TM disorder [4,5]. More recently this model re-emerged with the new focus on developmental abnormal or acquired occlusions producing pathological TM joint function in terms of internal derangements and pain. In the 1960s and 1970s another model became predominant. This model, the psychophysiological model, proposed that, except for obvious degenerative arthritic conditions and problems induced by external trauma, temporomandibular disorders were not due to occlusal abnormalities but had stress as a primary cause. Certain life stressors led to dysfunctional oral habits (clenching, grinding and related muscle tension) that created chronic muscle strain and facial pain. The constellation of symptoms involving pain, limited opening of the jaw and joint noises were called the myofascial pain dysfunction (MPD) syndrome [13,14]. Recent perspectives on temporomandibular disorders have proposed that they are multifactorial problems with structural (occlusion), functional (bruxism), external trauma, arthritic deterioration and psychological (anxiety, tension) factors as interrelated causes [7,18,20]. Furthermore, prompted by new anatomic and radiographic studies, Clark [3] suggested that TMD patients have many clearly different diagnostic problems including internal derangements, osteoarthritis and myoge-
nous disorders. These newer perspectives suggest that it is important to make a careful diagnostic evaluation of the multiple problems and symptoms of patients in order to appropriately select proper treatment approaches. There is some evidence that different treatments are helpful for patients with different types of TM disorder [2.3,10,11,17,19]. It seems that clarification of the involvement of psychological factors in different kinds of TM disorder patients is important; however, previous research on psychological differences between subgroups of TM disorder patients have not produced consistent results. Eversole, Stone, Matheson and Kaplan [9] compared 2 subgroups of TM disorder patients (a myogenic facial pain group and a TMJ internal derangement group) with a group of patients with atypical facial pain. Patients with myogenic facial pain scored higher on several MMPI scales, reflecting more distress, than did patients with internal derangements. On the other hand, Marbach and Lund [15] studied 3 subgroups of facial pain patients: myofascial pain dysfunction syndrome (MPD), arthritis of the temporomandibular joints and trigeminal neuralgia. Normal comparison groups were also studied. There were no differences in levels of distress between the myofascial pain dysfunction patients and those patients with degenerative arthritis. Both groups showed relatively normal levels of depression, measured with the depression scale of the Institute of Personality and Ability Testing questionnaire and average Spielberger State-Trait Anxiety Inventory scores. However, the MPD patients scored higher on a visual analog pain intensity scale than the TMJ arthritis patients. Dworkin, LeResche, Von Korff, Truelove and Sommers [8] used the Eversole et al. [9] diagnostic system as well as their own criteria to categorize patients seen in the clinic or a randomly sampled group of community cases with facial pain problems. Patients were fairly equally divided into those with myofascial pain dysfunction, internal derangements, and degenerative joint disease. The Eversole et al. [9] diagnostic categories were not related to levels of stress, anxiety, depression or somatic concern as measured by the Symptom Check List-90 (SCL-90). However, their own system found,that the diagnosis of MPD was associated with higher levels of anxiety, depression and somatization. The purpose of this article was to explore how diagnostic distinctions were related to the nature and extent of psychological factors in patients with TM disorders. Specifically, the study examined whether patients with a primarily myogenous disorder showed greater psychological distress in comparison to patients with internal derangements or other evidence of a primary articular disorder (i.e., osteoarthritis). Differences in pain levels among the subgroups were considered when examining psychological differences. This
study also explored the strength of the relationship between diagnostic categories and psychological factors by examining the accuracy of identifying diagnostic categories using the psychological variables as predictors.
Method The patients in the study were 112 consecutive patients seen at the UCLA TMJ and Facial Pain clinic, a university-based specialty clinic for TMJ and orofacial problems. The average age of patients was 39 years and there were no age differences among the diagnostic groups (described below). The overall sample was 86% female. Although there was a trend for fewer women in the myalgia group (77%), versus 93% in the mixed and 84% in the structural groups, there was not a significant difference in sex composition of the 3 diagnostic groups. The average number of months since the start of their TMD was 68 and there were no differences in chronicity among the diagnostic groups. Subjects were not included if they exhibited symptoms or history of a primary neurogenous disorder (trigeminal or postherpetic neuralgia); dental, periodontal or other orofacial infection; or an episodic vascular headache (e.g., cluster or migraine). The patients underwent a complete medical-dental history, clinical examination and were asked to fill out a number of psychological tests prior to their treatment at the clinic. The clinical examination consisted of a careful assessment of the range and quality of jaw movement difficulties, palpation of the muscles of mastication and TM joints and an evaluation of the occlusion. If clinical findings and symptom history indicated the need for a radiographic evaluation, this was also done. All radiographs were axially corrected sagittal tomograms taken in the closed and fully open mouth position. Based upon the above history and examination data, patients were grouped into 3 categories for this study. The first category consisted of patients with primary myalgia. Patients in this category showed substantial masticatory muscle pain symptoms on palpation but did not show joint pain on palpation, cIicking, crepitus or restriction of the normal condylar movement on mouth opening. More specifically, patients in this group reported: (1) moderate to severe tenderness upon palpation (3-5 lbs of pressure) in at least one masseter or temporalis muscle; (2) decreased pain-free jaw movement; and (3) full condyle translation and normal mouth opening was present with passive stretching of the jaw. Pain symptoms typically were described as dull, aching sensations which were continuous and of variable intensity. Characteristically, pain in the morning was worse
31
on awakening and frequently increased in the late afternoon and under conditions of increased stress. The second category of patients was those with a primary TM joint problem. These problems presented clinically as internal derangements or as osteoarthritis. Although these patients often showed evidence of mild to moderate myalgia, it was much less severe than the joint symptoms. The patients with internal derangement presented with primary symptoms of repeated, frequent clicking or popping of the temporomandibular joints on movement. The remaining patients in this group exhibited either TMJ osteoarthritis or internal derangement in the locking phase. The latter patients presented with primary symptoms of limited mouth opening (less than 40 mm interincisally including overbite even after passive stretching). The osteoarthritis patients presented with primary symptoms of TM joint region pain on palpation and movement and exhibited radiographically evident remodeling, flattening and/or spurring of the TM joint. These patients typically showed multiple joint noises or crepitus on movement. A third category of patients showed combined symptoms of both significant myalgia as well as evidence of a TM joint problem as defined above. For these patients the symptoms of myalgia were equal to or more severe than the joint symptoms. Measures A visual analogue scale (VAS) was used to assess the patients’ rating of their current pain level with anchor points at the left- (no pain) and right-hand (most intense pain imaginable) ends of a 100 mm horizontal line. Also, the McGill Pain Questionnaire (MPQ) was used to assess qualitative aspects of the patients’ pain. Patients described their pain by selecting an adjective descriptor from 20 categories and 3 scores were ob-
tained by summing the scale values for the sensory, affective and evaluative categories [ 16 1. Three self-report psychological tests were used to assess pretreatment levels of distress in these patients. These instruments were the Beck Depression Inventory (BDI), The Spielberger State-Trait Anxiety Inventory (STAI) and the Minnesota Multiphasic Personality Inventory (MMPI). The BDI is a 21 item self-rating measure of depression [l]. The State-Trait Anxiety Scale contains 2 subtests of 20 items each, measuring either state or trait anxiety [22]. The MMPI is a 566 item true-false inventory which has many different scales assessing a variety of psychological problems. The MMPI is interpreted by examining scores on the validity scales (L, F and K) which assess the person’s approach to taking the test (i.e., careless or -random responding, faking bad, minimizing faults). The interpretation of psychological difficulties is made by examining scores on the clinical scales which include: hypochondriasis (Hs), which measures concern about bodily functioning; depression (D), which assesses feelings of depression, helplessness, hopelessness; hysteria (Hy), which assesses somatic concerns and denial of emotional or interpersonal problems; and psychasthenia (Pt), which measures ruminations, worry and anxiety. Other clinical scales assess impulsivity and low frustration tolerance (Pd), suspiciousness and distrust (Pa), alienation and confusion (SC) and high energy level and distractability (Ma).
Results Table I presents the psychological scores on the Beck Depression Scale, the Spielberger State/Trait Anxiety Scales and the MMPI scores of the 3 diagnostic groups.
TABLE I BECK DEPRESSION, STATE/TRAIT ANXIETY, ANCE FOR THE DIAGNOSTIC GROUPS Myalgia
(N = 27) Beck
11.6 (1.56)
State anxiety
70.8 (5.70)
Trait anxiety
72.7 (6.24) 72.0 (2.68) 66.5 (2.47) 72.4 (2.14) 63.3 (2.14)
MMPI Hs MMPI D MMPI Hy MMPI Pt
AND MMPI MEAN SCORES, (STANDARD
Combined (N = 37)
TM joint (N = 42)
10.8 (1.33) 58.3 (4.96) 60.7 (5.28) 64.6 (2.13) 61.9 (1.97) 67.6 (1.71) 57.8 (1.70)
6.0 (1.25) 51.3 (4.65) 54.4 (4.94)
ERRORS),
F
AND ANALYSIS
P
5.14
0.01
3.51
0.05
2.67
0.07
56.5 (2.03)
11.02
0.001
56.5 (1.87)
5.46
0.01
59.3 (1.61)
13.14
0.001
55.9 (1.62)
3.85
0.02
OF VARI-
TABLE
II
PAIN SCORE
MEANS.
(STANDARD
ERRORS)
AND ANALYSIS
MPQ affective MPQ evaluative Pain VAS
,
TM joint (N = 47)
F
P
12.0 (1.87) 6.4 (1.15) 2.0 (0.32) 50.6 (5.05)
13.5 (1.57) 3.0 (0.97) 2.2 (0.27) 48.0 (4.33)
7.2 (1.49) 2.4
4.64
0.01
4.09
0.02
1.59
0.21
6.66
0.01
MMPI Scores of Diagnostic Groups
I
GROUPS
Combined (N = 36)
Fig. 1 presents a graph of the MMPI clinical scale scores of the 3 diagnostic groups. There were statistically significant differences between the mean scores of the diagnostic groups on several of the distress measures based on a standard one-way ANOVA. In general, patients with primary myalgia scored higher on these scales than the other 2 groups. Patients with a combined diagnosis consistently showed scores in between those of the myalgia and TM joint subgroups. Table II presents the mean pain scale scores of the various diagnostic groups. There were statistically significant differences between the diagnostic categories on the McGill Pain Questionnaire sensory and affective scores as well as on a visual analog pain intensity scale based on one-way ANOVA. Patients with myalgia scored on average higher on these measures of pain than patients with TM joint problems. Patients with a combined diagnosis consistently had average scores between the myalgia and the TMJ problem patients with the exception of the MPQ evaluative score. In order to assess whether pain levels accounted for the differences between the subgroups on the various distress measures, analysis of covariance was performed with the pain intensity score as the covariate. Two of the scores on the psychological scales remained statisti-
300
FOR THE DIAGNOSTIC
(N = 26)
Myalgia
MPQ sensory
OF VARIANCE
(0.90) 1.6 (0.25) 30.2 (4.04)
tally
significant
(Hs:
F = 5.4, P < 0.01;Hy: F = 7.2,
P < 0.01). However, Pearson correlations between pain scores and the various psychological variables were not consistent across the 3 diagnostic subgroups (see Table III). In the myalgia patients, pain intensity was not correlated with depression and anxiety scores while it was related to the MMPI Hs and Hy scales. Pain was consistently related to the psychological scores in the TM joint problem subgroup. In the combined diagnosis group there were high correlations between pain and depression scores. In order to account for these divergent patterns of correlations among the diagnostic groups, additional covariates were added to the analyses of covariance. The additional covariates, interactions between the pain and the diagnostic group variates, allow for non-parallel lines for the 3 diagnostic groups in the analysis of covariance model. The difference between the groups on the Hy scale (F = 5.32, P < 0.01) remained significant. Discriminate analysis was performed to assess the nature and extent of the relationship between psychological factors and differences among the diagnostic groups. Linear discriminate functions were used to combine the psychological variables in order to predict diagnostic group membership. The 4 MMPI scales (Hs, D, Hy and Pt) that significantly differentiated the groups on a univariate basis were used as the predictors. Sev-
90 I
TABLE
III
CORRELATIONS OF PAIN VAS WITH BECK DEPRESSION, STATE/TRAIT ANXIETY, AND MMPI Hs, D, Hy AND Pt SCORES AMONG THE THREE DIAGNOSTIC SUBGROUPS
4c
!
0
0
o-o
Combined
0
My0kp 0
TMJ
JO_-,
Fjs
D
Hy
Pd
Pa
Pt
SC
Ma
Fig. 1. MMPI clinical scale scores of the 3 diagnostic groups. There were statistically significant differences between the mean scores of the diagnostic groups on several of the distress measures based on a standard one-way ANOVA.
Beck State anxiety Trait anxiety MMPI Hs MMPI D MMPI Hy MMPI Pt
Myalgia
Combined
TM joint
0.09 - 0.08 -0.16 0.49 0.07 0.50 - 0.06
0.52 - 0.04 0.04 0.31 0.42 0.07 0.19
0.30 0.25 0.25 0.48 0.18 0.45 0.39
33
enty-four percent of the patients with a structural diagnosis were correctly identified using their psychological scores. On the other ‘hand, dnly 46% of the myalgia patients were correctly categorized based upon psychological scores. In general, 58% of all patients were correctly assigned to their actual diagnostic group. Thirteen percent of patients were incorrectly identified as either myalgia patients or TM joint patients when their actual diagnosis was TMJ problem or myalgia. The other incorrect predictions (29%) were misclassified as combined versus one of the other 2 diagnostic categories.
Discussion
The results of this study are consistent with those found by Eversole et al. [9] and Dworkin et al. [8] (using their own diagnostic system) who reported more distress m patients with MPD diagnoses versus those with internal derangements. Our findings are also consistent with the Marbach and Lund [15] report of higher pain levels in MPD versus TMJ arthritis patients; however, the present results are inconsistent with their finding of similar levels of depression and anxiety in MPD versus TMJ arthritis patients. The absence of differences in the Marbach and Lund study could be due to inclusion of some patients with structural difficulties in their MPD group. The statistically significant psychological differences among the various diagnostic groups were not strong enough for clinical use in accurately categorizing patients; nevertheless, the differences appeared to have etiological implications. The pattern of scores on pain and distress measures in myalgia patients is consistent with a psychophysiological model of disorder for them. The myalgia group contained large numbers of patients with high levels of distress and pain. However, higher degrees of anxiety and depression were not associated with higher pain levels. Furthermore, these patients showed higher scores on measures of concern about bodily functioning and preoccupation with illness that were not accounted for by differences in pain levels. When myalgia patients are in pain and are preoccupied with worries about physical functioning and fearful about something going wrong with their body, they seem to be avoiding dealing with distressing aspects of their life. This suppression of emotional difficulties may contribute to excess muscle tension and may facilitate dysfunctional oral habits like clenching and bruxing. Since these patients have high levels of pain and distress, they seem to need treatments designed to help them acknowledge stressful life problems and to learn methods to improve their ability to cope with their pain and stress problems. Patients with primary TM joint problems showed
low levels of psychological difficulties consistently across various measures used in this study as well as low to moderate correlations between psychological scores and pain levels. As a group these patients do not show much evidence of psychological difficulties; however, when they are in pain they experience increasing distress. Their distress appears to be a response to the difficulties in coping with the pain precipitated by structural pathology. This process is consistent with a biomechanical model in which structural pathology leads to discomfort and functional difficulties and a distressful emotional reaction. These patients may need stress management yet clearly the first choice in treatment should be therapies directed to their structural problem (i.e., bite appliances, physical therapy, etc.). Patients with a combined diagnosis present more difficulties in making judgments about psychological etiology. Their relatively high Beck Depression scores and their correlations between pain and depression suggest that they are reacting to their pain problems with some depression. They may benefit from combinations of stress management and somatic treatments. It is interesting to compare the above findings with similar studies of headache patients. Kudrow and Sutkus [12] compared MMPI scores of 3 categories of headache patients: migraine, mixed and muscle contraction. They found higher scores on the neurotic triad (Hs, D and Hy) in the muscle contraction patients. The authors speculated that differences in the impact of the pain problem in the person’s life might account for the higher MMPI scores of the muscle contraction patients. In a similar manner, perhaps patients with myalgia are experiencing more stressful life circumstances and more negative illness impact. Research is needed to compare the various diagnostic subgroups in terms of life stress and illness impact.
Acknowledgement
Preparation of this article was supported by Grant DE07618 from the National Institute of Dental Research.
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