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Negative cognitions of dental phobics: Reliability and validity of the Dental Cognitions Questionnaire
Behav. Res. Ther. Vol. 33, No. 5, pp. 507-515. 1995
Pergamon
ElsevierScienceLtd. Printed in Great Britain
0005-7967(94)00081-6
NEGATIVE RELIABILITY
COGNITIONS AND
COGNITIONS
OF
DENTAL
VALIDITY
OF
THE
PHOBICS: DENTAL
QUESTIONNAIRE
A. D E J O N G H , 1. P. M U R I S , 2 N. S C H O E N M A K E R S I and G. T E R H O R S T l LDepartment of Social Dentistry and Dental Health Education, Academic Centre for Dentistry Amsterdam, Louwesweg 1, 1066 EA Amsterdam and 2Department of Experimental Abnormal Psychology, University of Limburg, P.O. Box 616, 6200 MD Maastricht, The Netherlands (Received 27 August 1994)
Summary--This study investigated the psychometric properties of the Dental Cognitions Questionnaire (DCQ). This measure contains 38 items and assesses both frequency and believability of negative cognitions related to dental treatment. The results indicated that the DCQ has good internal consistency, high test-retest reliability, and satisfactory concurrent validity, as indicated by positive associations with indices of anxiety and other cognitive measures (n = 180). Factor analysis revealed a one factor solution. Furthermore, the DCQ discriminated strongly between dental phobics (n = 85) and non-phobic Ss (n = 70). Moreover, it was found that combinations of DCQ items have substantially more explanatory power than did a measure of dental trait anxiety, explaining up to 70.7% of the variance in state anxiety ratings in the dental situation. Overall, it appears that dental phobics have many extremelynegativebeliefs and self-statements about themselves and about what might happen during treatment. Since certain cognitions seem to play a critical role in fear evocation, diminishing catastrophizing ideation may be an important determinant of adjustment to dental treatment and reduction of psychological distress.
INTRODUCTION The prevalence of dental anxiety and dental phobia in modern western societies is high. The results of research in North-American (e.g. Milgrom, Fiset, Melnick & Weinstein, 1988), Asian (e.g. Domoto, Weinstein, Melnick, Ohmura, Uchida & Ohmachi, 1988), and European populations (e.g. Schuurs, Duivenvoorden, Thoden van Velzen & Verhage, 1984; Stouthard & Hoogstraten, 1990) all indicate that about 40% of people are afraid to visit the dentist, 20% are highly anxious, whereas 5% are so anxious that dental treatment is avoided. Meanwhile, it is a well-established fact that dental anxiety and, in its wake, avoidance of dental treatment have detrimental effects on health (e.g. McGlynn, Gale, Glaros, LeResche, Massoth & Weiffenbach, 1990; Hakeberg, Berggren & Gr6ndahl, 1993). In recent years, both theorists and therapists have more and more advanced the idea that cognitive phenomena are important for the understanding of anxiety disorders (see e.g. Beck, 1976; Foa, Steketee & Rothbaum, 1989; Eysenck, 1992). According to Beck's (1976) cognitive model, emotional problems are accompanied by negative patterns in which individuals think about themselves and the external world. As far as anxiety and phobia in general are concerned, the negative patterns of thinking are centred around danger and harm (e.g. Beck, Laude & Bohnert, 1974). Support for the applicability of the cognitive approach to dental anxiety was provided by de Jongh and colleagues (de Jongh & Ter Horst, 1993; de Jongh, Muris, Ter Horst, Van Zuuren & de Wit, 1994; de Jongh, Muris, Ter Horst & Duyx, 1995). In these studies, it was found that dental anxiety is strongly associated with the tendency to experience negative or threatening thoughts. Although these findings make it difficult to tease out cause and effect, they suggest that negative thinking patterns play a crucial role in fear evocation. For example, while being treated a dental patient may think: "This dentist will drill in my tongue or cheek". If so, it is conceivable, that this person is apprehensive and difficult to treat. Moreover, it may be that this person will *Author for correspondence. 507
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not easily comply with techniques aimed at reducing anxiety reactions, such as relaxation or hypnosis. Anxiety level may even be heightened, if for instance, this person believes that relaxing makes him more vulnerable to the dentist's drill. Since it seems relatively easy to gather information about the occurrence of negative beliefs and self-statements (de Jongh & Ter Horst, 1993), this might be a useful way to gain understanding about the processes involved in maintenance of dental anxiety. Empirical evidence demonstrates that the occurrence of negative and catastrophic thoughts is not the only cognitive factor involved in dental anxiety. For example, the extent to which people believe to have control over their negative thoughts appears to be an equally important mediating factor. Kent and Gibbons (1987) found that highly anxious dental patients not only reported a greater number of negative thoughts, but also stronger efforts to control (i.e. to suppress) these thoughts as the appointment came closer in comparison with their low anxious counterparts. In a previous study (de Jongh et al., 1994), it was found that frequency of negative cognitions and degree of control, as indexed by questionnaires, together accounted for 75% of the variance in dental trait anxiety scores. Another seemingly likely, but yet unverified cognitive factor related to dental anxiety is the extent to which patients believe their negative cognitions. Plausibly, the patient who thinks that the dentist will drill in his cheek or tongue and perceives this event as most likely is more anxious than someone who thinks the prebability of such an event is low. Evidence for the contention that believability is associated with levels of anxiety has been derived from studies among people suffering from various types of anxieties. For example, spider phobics strongly believe various catastrophic and irrational ideas about spiders and encounters with spiders (Arntz, Lavy, van den Berg & van Rijsoort, 1993). In addition, Ss whose claustrophobia was reduced after therapy reported a significant reduction, not only in the number of negative thoughts but also in the believability of these thoughts (Shafran, Booth & Rachman, 1993). Thus, severity of dental anxiety may be associated with the degree of belief in negative cognitions. In order to better understand the cognitive characteristics of dental patients and their relationship with anxiety, research should aim at developing instruments that are specifically sensitive to assess the cognitive features seen as operative in the maintenance or exacerbation of dental anxiety. The aim of the present study was to examine the psychometric properties of such cognitive measure, the Dental Cognitions Questionnaire (DCQ), which was designed to assess frequency and believability of cognitions related to dental treatment. This questionnaire was constructed on the basis of the results of an earlier study exploring thought content among dentally anxious patients (De Jongh & Ter Horst, 1993), and studies examining differences in thought content between individuals high and low in dental anxiety (de Jongh et al., 1994; de Jongh et al., 1995; Kent & Gibbons, 1987). METHOD Subjects
For psychometric evaluation, the DCQ was applied to the following three S groups: (l) A university student group consisting of 180 first-year undergraduate students of the University of Amsterdam. As part of their study requirements, the Ss completed a large set of questionnaires, including the DCQ. Ss were excluded from the study if they never had been treated by a dentist (at least one filling). The number of remaining Ss was 151 (95 women, mean age = 21.9; 56 men, mean age = 24.4). They were regular dental patients, i.e. they indicated to comply with a schedule of dental check-ups every six months as is required by the Dutch national health insurance. (2) A group of dental phobics consisting of 85 patients (44 women) who awaited treatment in a dental fear clinic in Amsterdam. All patients had a history of avoiding dental treatment for several years (M = 8.5 years, SD = 9.0, range 1-34). Mean age of this group was 31.6 years (SD = 8.2, range 18-62). All patients were requested to complete various mailed questionnaires, including the DCQ. They were put on a waiting list as soon as the questionnaires had been returned to the clinic. A subsample of the phobic group participated in a study in which the effects of a cognitive
Negative cognitions of dental phobics
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restructuring intervention were investigated. Since these patients had to rate their state anxiety in the dental situation, it was possible to assess the ability of the DCQ to predict state anxiety in the dental situation. In order to avoid confounding of treatment and occurrence of cognitions only the data of the patients (n = 31) who did not receive the cognitive intervention were used.* (3) A second group of first-year psychology students of the University of Amsterdam (n = 70; 58 women), who served as non-phobic control group for the dental phobics. The students had a mean age of 20.7 years (SD --- 2.2, range 18-28) and were all regular dental attenders (check-ups at least every six months). They received course credit points for the participation in the study.
Measures The Dental Cognitions Questionnaire (DCQ) consists of 38 negative cognitions (beliefs and self-statements) related to dental treatment. The first section of the questionnaire contains a list of 14 negative beliefs pertaining to dentistry in general (e.g. "Dentists don't care when it hurts") and to the patient himself (e.g. "I can't stand pain"). Following the sentence: "When knowing that I have to undergo dental treatment very soon, I think . . . " , Ss are asked to tick "Yes" or " N o " for each item. The second section consists of 24 negative self-statements that pertain to thinking during treatment (e.g. "Everything goes wrong"). Following the sentence: "While being treated, I t h i n k . . . " , Ss are again asked to tick "Yes" or " N o " for each item. In addition, Ss are instructed to rate the degree to which he/she believes each statement at that moment by filling in a percentage (0% = "I don't believe this thought at all" to 100% = "I am absolutely convinced that this thought is true"). "Yes"-responses on the items are summed to give a total negative cognition score (range 0-38). For each S, also a mean percentage believability score is computed. The following other measures were employed: The Dental Anxiety Scale (DAS; Corah, 1969) is a four-item self-report scale that has been widely used for measuring dental trait anxiety. Items are scored on a scale of 1 to 5 and summed to give an overall anxiety score ranging from 4 (not anxious at all) to 20 (extremely anxious). Cronbach's alpha of the DAS in the present sample was 0.95. The State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch & Lushene, 1970; van der Ploeg, Defares & Spielberger, 1980) consists of two separate self-report scales for measuring both trait anxiety and state anxiety. The STAI A-Trait scale (20-items) asks people to describe how they generally feel. The STAI A-State scale (20-items) requires people to describe how they feel at a particular moment in time. Cronbach's alpha's of the STAI scales in the present sample were both 0.92. The Irrational Beliefs Inventory (IBI; Koopmans, Sanderman, Timmerman & Emmelkamp, 1994) is a 50-item inventory measuring a wide range of irrational beliefs. The IBI consists of five subscales (problem avoidance, rigidity, worrying, need for approval and emotional irresponsibility). For the purpose of the present study only the worrying scale (12 items concerning worrying over possible misfortune and possible future accidents) was used. People are asked to indicate the extent to which they agree with each of the beliefs, from 1 (strongly disagree) to 5 (strongly agree). The score can be obtained by summation of the items. Cronbach's alpha of the scale in the present study was 0.87. State anxiety/tension was assessed with 100 mm visual analogue scales ranging from 0 (not at all anxious/tense) to 100 (very anxious/tense). Patients were asked to rate their anxiety upon arrival in the dentist's waiting room and while sitting in the dental chair. For dentist's rating of patient's anxiety also 100 mm visual analogue scales ranging from 0 (not at all anxious/tense) to 100 (very anxious/tense) were used.
Procedure Internal consistency, item-total correlation, and test-retest reliability were computed on the DCQ scores of the 180 students. The DCQ was administered two times with an interval of five weeks. Furthermore, to test concurrent validity, correlations between the DCQ and a number of other questionnaires, including the STAI, DAS, and IBI-worrying were calculated. *Initially this group consisted of 37 patients, but 6 patients were excluded because of missing data.
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Table I. Mean scores (and standard deviations) on the DCQ, DAS, STAI, and IBl-worrying including correlations between these measures for the student sample (n = 180)
STAI A-trait IBI-worrying DAS DCQ-frequency DCQ-believability Mean SD
STAI A-state
STAI A-trait
IBI-worrying
DAS
DCQ frequency
0.61" 0.55* 0.13 0.27* 0.23*
0.71" 0.26* 0.32* 0.31 *
0.28* 0.36* 0.22*
0.55* 0.36*
0.58*
8.6 2.9
9.8 6.9
35.8 10.0
38.2 9.8
33.3 8.7
DCQ believability
23.9 16.4
Note: *Significant at P < 0.05. STAI = Spielberger's State Trait Anxiety Inventory; IBI = Irrational Beliefs Inventory; DAS = Dental Anxiety Scale; DCQ = Dental Cognitions Questionnaire.
To assess discriminant validity DCQ scores of the dental phobics and the second group of students (non-phobic controls) were compared. The non-phobic Ss came in groups of 6 to an experimental room to complete the questionnaires. Predictive validity was examined by exploring the relationship between DCQ scores and dental state anxiety in a subsample of the phobic group. After filling out several questionnaires at home, including the DCQ, and a waiting period of at least one month these patients were phoned to make an appointment with one of the dentists. They were told that their first appointment only concerned a conversation about their dental anxiety and a check-up. At their visit to the dentist, in the waiting room of the dentist all patients were again asked to complete a set of questionnaires, including a visual analogue scale for ratings of state anxiety. Next, the patients were escorted to the dentist. During this first visit the dentist and the patient talked about patient's anxiety and then the dentist carried out a check-up. Before starting the check-up, while sitting in the dentist's chair, patients were asked to rate state anxiety again on a visual analogue scale. When the appointment was over, the dentist also rated patient's anxiety/tension. RESULTS
Reliability and dimensional structure Table 1 shows the means and standard deviations of the DCQ and the various other measures for the student group. An unpaired t-test showed that the frequency scores on the DCQ were significantly [t(149)=2.7, P <0.01] higher for women (M = 11.0; S D = 7.0) than for men (M = 7.9; SD = 6.4). No significant differences between the believability scores of women and men were found. Internal consistency was estimated by calculating Cronbach's alpha on the scores of the Ss at the first time they filled out the DCQ. The overall alphas for the full scale* were 0.89 for DCQ-frequency and 0.95 for DCQ-believability. The average item-total correlation for the scale was 0.45 with a range of r = 0.21, P < 0.01 (item 9) to r = 0.63, P < 0.001 (item 15). Test-retest reliability for the DCQ over a five week period in the non-anxious sample was evaluated using Pearson correlations and was 0.83. An exploratory principal component factor analysis with varimax rotation was performed on the DCQ items. A factor analysis performed on the frequency scores identified 13 factors with eigenvalues exceeding 1.0, together representing 65.9% of the variance. An exploratory factor analyses on the believability scores extracted seven factors with eigenvalues larger than !.0, which together accounted for 63.8% of the variance. However, inspection of the scree plots (Cattell, 1978) suggested a general one-factor model. Factor analyses performed on the data of men and women separately indicated similar patterns of results. Concurrent validity The relation between DCQ and STAI, DAS, and IBI-worrying were assessed using Pearson correlation coefficient (see Table 1). All measures were found to be significantly correlated, the only exception being the correlation between DAS and STAI-Trait (r = 0.13, P > 0.05). The correlation * B o t h sections (beliefs a n d self-statements) were r e g a r d e d as o n e scale since the s u m scores o f b o t h sections w e r e significantly c o r r e l a t e d ( f r e q u e n c y r = 0.65, P < 0.001 a n d believability r = 0.74, P < 0.001).
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between the frequency and believability scores of the DCQ was significant (r = 0.58, P < 0.001). Results revealed an acceptable level of validity. The magnitude of the correlations between the two DCQ subscales and a measure of dental trait anxiety (DAS) were both higher than the correlations between DCQ and measures of general trait anxiety or state anxiety. In addition, the correlations between DCQ and the worrying scale of the IBI were rather modest. These findings suggest that the DCQ taps unique (cognitive) aspects of anxiety related to the dental setting and not just trait anxiety or worrying about future events in general.
Discriminant validity Evidence for discriminant validity was derived by comparing DCQ scores of phobic and non-phobic persons. The questionnaire data were subjected to a series of 2 (sex: men/women) x 2 (group: phobic/non-phobic) analyses of variance (ANOVAs). An ANOVA performed on the DAS scores revealed a main effect of group [F(1,151)= 237.5, P < 0.001], indicating that, as expected, the phobic Ss had significantly higher dental trait anxiety scores (M = 17.6; SD = 2.2) than their non-phobic counterparts (M = 9.6; SD = 3.2). As for the DCQ frequency scores, the ANOVA also revealed a main effect of group [F(1,151) = 101.2, P < 0.001], indicating that the mean number of reported cognitions was significantly higher in the phobics (M = 22.5; SD = 6.7) than in the non-phobic controls (M = 10.0; SD = 7.0). The same was true for the mean believability rating (M = 50.1; SD = 16.3 vs M = 19.4; SD = 11.7), [F(1,151) = 130.6, P < 0.001]. No significant main effects of sex or interactions of group with sex were found. Since phobic and non-phobic groups differed significantly with respect to age the 2 × 2 ANOVAs were conducted again, this time only using age-matched groups (Ss between 18-24 years). A comparison of these groups essentially revealed the same pattern of results: phobic and non-phobic Ss scored significantly different on dental trait anxiety (DAS) [F(1,69)= 66.9, P < 0.001], frequency of cognitions [F(1,69)= 47.5, P < 0.001], and believability of cognitions [F(1,69) = 75.0, P < 0.001]. Again, no main effects of sex, nor interactions of sex with group were found. To determine which items contribute to the differences found in total DCQ scores, additional analyses were carried out. First of all, chi-square analyses were performed to compare the proportions of Ss in the phobic and non-phobic group who reported each of the 38 cognitions. In addition, a series of independent t-tests was computed comparing both groups with respect to mean believability of the cognitions. Bonferroni correction for multiple tests yielded a significance level of 0.0013 when an overall level of 0.05 was employed. All items, with proportions, means and standard deviations, are presented in Table 2. As can be seen, most cognitions were found to discriminate between both groups when the Bonferroni corrected level was employed. All but four items were more frequently endorsed by the phobic than by the non-phobic group, while for all items believability was found to be significantly higher in the phobic group than in the non-phobic group. In both groups item 16 ("This treatment will hurt") was most often reported (87.1% in the non-phobic group and 96.5% in the phobic group) and most strongly believed (mean believability in the non-phobic group 53.6% vs 83.6% in the phobic group). In the phobic group item 5 ("Dentists are often incapable") was least often reported (12.9%), while in the non-phobic group item 28 ( ' I will die during treatment") was least often indicated. Regarding the latter item, 14.1% of the phobic group patients indicated that this thought may occur to them during treatment, while in the non-phobic group only 1.4% of the patients indicated that during treatment this thought may pop into their head. In both groups the believability of this item was lowest (mean believability: 1.4% in the non-phobic group vs 18.2% in the phobic group).
Predictive validity To assess predictive validity the degree of relationship between patients' DCQ frequency scores and state anxiety ratings in the dental situation was assessed. The following three measures of state anxiety were used: self-reported anxiety in the waiting room, self-reported anxiety in the dental chair, and anxiety as rated by the dentist. First, the inter-relationships between the various ratings of patient's anxiety were computed. Dentists' ratings of patients' level of anxiety during the first meeting was found to be significantly (r = 0.48, P < 0.05) related to patients' self report of anxiety in the dental chair, but not with their
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Table 2. Proportions of subjects who reported DCQ cognitions and means (standard deviations) of DCQ-believability scores, for phobic and non-phobic patients. P values pertaining to group differences are given Non-phobic group (n = 70)
Phobic group (n = 85)
Frequency %
Believability M (SD)
Frequency %
Believability m (SD)
P Frequency
P Believability
30.0 21.4 21.4 14.3 18.6 28.6 20.0 17.1 8.6 24.3 50.0 28.6 25.7 7.1
31.7 (27.0) 19.7 (19.1) 16.2(17.1) 15.9 (18.7) I 0.3 (12.4) 21.4 (20.0) 18.4 (I 5.7) 10.1 (16.9) 6.6 (14.6) 22.4 (28.8) 39.4 (30.8) 27.3 (26.5) 21.9 (26.7) 7.8 (14.1)
60.0 70.6 48.2 64.7 12.9 78.8 41. I 62.4 61.2 68.2 71.8 69.4 62.4 16.5
45.2 (34.8) 47.8 (28.8) 37.8 (30.2) 45.0 (29.4) 19.5 (28.5) 59.5 (32.1) 35.0 (32.5) 53.3 (39.1) 57.1 (40.4) 64.9 (36.6) 68.5 (34.3) 60.0 (33.3) 54.0 (36.9) 14.7 (28.7)
0.001 0.001 0.001 0.001 0.460* 0.001 0.008 0.001 0.001 0.001 0.009 0.001 0.001 0.130"
0.005 0.001 0.001 0.00 I 0.007 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.034
17.1 87. I 17. I 32.9 27. I 38.6 11.4 15.7 24.3 58.6
9.7 (16.7) 53.6 (28.9) 14.6 (20.5) 19.2 (23.1) 24.1 (29.2) 25.1 (27.9) 12.4 (17.5) 13.9 (21.2) 14.1 (20.3) 39.0 (29.9)
45.9 96.5 54.1 63.5 78.8 80.0 63.5 56.8 71.8 92.9
39.4 (35.7) 83.6 (25.2) 48.6 (38.0) 49.4 (36.0) 70.3 (33.4) 71.0 (34.8) 60.3 (36.3) 53.8 (39.1) 52.1 (37.1) 80.2 (31.4)
0.001 0.062* 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001
0.001 0.001 0.00 I 0.00 I 0.001 0.001 0.001 0.001 0.001 0.001
27. I 67.1 44.3 1.4 17.1 5.7 7.1 55.7 37.1
18.2 (24.8) 40.6(30.2) 29.6 (30.0) 1.4(7.4) 14.4(23.0) 8.8 (17.5) 4.3 (10.8) 32.5 (30.1) 27.9 (26.2)
45.9 80.0 81.2 14.1 70.6 34.1 29.4 83.5 68.2
34.7 (35.5) 66.5(35.1) 78.4 (30.0) 18.2(34.9) 59.8(34.1) 31.3 (35.5) 25.1 (36.1) 62.1 (31.7) 58.8 (39.3)
0.026 0.102" 0.001 0.011 0.001 0.001 0.001 0.001 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0,001 0,001
10.0 18.6 17.1 10.0
11.6 (16.1) 10.7 (15.9) 15.1 (19.6) 5.5 (10.2)
30.6 41.2 56.5 28.2
30.0 (36.1) 31.1 (32.9) 43.6 (38.2) 24.6 (29.9)
0.001 0.004 0.001 0.008
0,001 0.001 0.001 0,001
37.1
22.1 (26.1)
88.2
67.5 (34.3)
0.001
0,001
Beliefs about oneself and dentistry in general I. 2. 3. 4. 5. 6. 7. 8. 9. 10. II. 12. 13. 14.
Dentists do as they please Dentists are often impatient The dentist does not care if it hurts Dentists do not understand you Dentists are often incapable Dentists think you act childish Treatments often fail My teeth can't be saved I should be ashamed about my teeth My teeth might break I can't stand pain I am a tense person I am a difficult person l am someone with very long roots
Self-statements during treatment 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38.
Everything goes wrong This treatment will hurt My teeth will break Something surely will go wrong It never runs smoothly I am helpless I can't control myself l can't escape, I'm locked in Anaesthetics often do not work The sound of the drill frightens me The dentist will drill in my tongue, gums or cheek The nerve will be touched have no control over what happens will die during treatment will panic daring treatment will faint during treatment will suffocate during treatment can't stand this treatment for long will certainly have pain afterwards The filling will certainly fall out and has to be made again This treatment fails I become sick The dentist will lose control over his drill The dentist believes that I am a difficult patient and act childish
Note: Except items marked with * all Ps < 0.05.
anxiety ratings in the waiting room (r = 0.35, P > 0.05). Furthermore, between patients' selfreported level of state anxiety in the waiting room and in the dental chair a significant correlation was found (r = 0.50, P < 0.05). Next, it was determined which combination of DCQ items maximized the prediction of state anxiety in the dental situation. It was also examined whether dental trait anxiety could further improve the prediction of patients' state anxiety. Therefore, a series of separate stepwise multiple regression analyses were conducted with the scores on the DCQ items and dental trait anxiety being predictors, and the various state anxiety scores being dependent variables. To control for gender and the fact that a subsample of 14 patients had visited a dental hygienist,* these two variables were forced into the equations. It appeared that DCQ-items 16 ("This treatment will hurt") and 24 ("The sound of the drill frightens me") had no variance, since all patients indicated that these thoughts would occur during treatment. Consequently, the analyses were executed without these items. Table 3 shows the items that contributed significantly to the prediction of patients' anxiety in the dental situation. As can be seen, in only one case prediction of state anxiety could be significantly improved by the addition of dental trait anxiety score. A combination of three *The d e n t a l h y g i e n i s t d i d n o t t r e a t these patients, b u t p r o v i d e d t h e m o n l y with i n f o r m a t i o n a b o u t o r a l h e a l t h a n d p r e v e n t i v e behaviours.
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cognitions significantly contributed to the prediction of state anxiety in the waiting room, explaining 61.9% of the total variance. With regard to self-reported anxiety in the dental chair a combination of five different DCQ items and the DAS score were entered into the equation. These variables together explained 70.7% of the variance in the criterion. As to the prediction of dentist's rating of patients' state anxiety, it was found that five different negative cognitions contributed significantly to the regression equation, explaining 70.4% of the variation in state anxiety ratings. The largest contribution was made by the belief "Dentists think you act childish".
DISCUSSION The current study examined reliability and validity of the DCQ, a self-report instrument designed to assess both occurrence and believability of negative cognitions related to dental treatment. The DCQ appeared to possess sufficient internal consistency, high test-retest reliability and demonstrated adequate concurrent validity, as judged by its correlations to other measures of either dental trait anxiety, general trait anxiety and worrying. Discriminant validity of the DCQ was supported by comparing the scores of phobic and non-phobic individuals. It was found that phobic patients not only reported a higher frequency of negative and catastrophic cognitions than non-phobic controls, they also showed a greater degree of believe in their negative thoughts. An inspection of the content of the thoughts of dental phobic individuals reveals that many thoughts pertain to ideas about suffocating or loss of control, and thus strongly resemble those held by panic patients (e.g. Street, Craske & Barlow, 1989), or individuals suffering from other type of phobias (e.g. Arntz et al., 1993; Shafran et al., 1993). This may be due to the fact that dental phobia is a diagnostically heterogeneous group. A recent study (Roy-Byrne, Milgrom, Khoon-Mei, Weinstein & Katon, 1994) indicated that 40% of a sample of phobic dental patients had a current diagnosis other than simple phobia. Thus, patients suffering from severe dental anxiety may in fact demonstrate characteristics of another anxiety disorder such as panic disorder. The present findings also provided evidence for predictive validity of the DCQ. It was found that a number of negative cognitions contributed significantly to the prediction of state anxiety in either waiting room (61.9%) or dental chair (70.7%). Such proportions of explained variance are remarkably high considering the fact that most patients filled out the DCQ more than one month before they visited the dentist. Combinations of specific negative beliefs and negative selfstatements appeared to have substantially more explanatory power than did the score of a situation specific measure of trait anxiety, the Dental Anxiety Scale (DAS). The fact that the prediction of anxiety in the dental situation could largely be explained by occurrence of particular combinations of negative cognitions strongly suggest that negative Table 3. Results of a series of stepwise regression analyses with patient's anxiety being the dependent variable (n = 31)*
df
F
Cumulative % variance
3, 27
8.6
43.3
4, 28 5, 25
9.1 10.4
51.9 61.9
Prediction of self-reported state anxiety in the dental chair I. "I am helpless" (20) 2. "'The dentist will drill in my tongue, gums or cheek" (25) 3. "'I can't control myself" (21) 4. "I can't stand pain" (11) 5. "Dentists think you act childish" (6) 6. DAS score
3, 4, 5, 6, 7, 8,
26 25 24 23 22 21
4.2 5.4 6.1 7.4 8.3 10.1
24.0 36.9 45.8 56.3 63.0 70.7
Prediction of state anxiety in the dental chair as rated by the dentist: I. "Dentists think you act childish" (6) 2. "I become sick" (36) 3. "Dentists are often impatient" (2) 4. "I can't stand pain" (1) 5. "It never runs smoothly" (19)
3, 4, 5, 6, 7,
26 25 24 23 22
8.5 10.1 10.2 10.5 10.8
43.8 55.6 61.4 66.2 70.4
Order of entry
Variable
Prediction of self-reported state anxiety in the waiting room: 1. " M y teeth might break" (10) 2. "The dentist believes that I am difficult patient and act childish" (38) 3. "'I become sick" (36)
Note: *After controlling for gender and appointment with dental hygienist.
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thinking patterns play a crucial role in fear evocation. The present findings, therefore, support Beck's notion that cognitions pertaining to the situation and their own resources have an effect on behaviour and result in increased psychological distress (e.g. Beck, 1976; Beck, Emery & Greenberg, 1985). In the dental situation, thoughts such as " I am helpless" may increase patients' sense o f vulnerability and heighten anxiety level. In turn, the dental patient may interpret his anxiety, and certain bodily sensations, as signs that he does not have control over himself and become in grip o f ideas such as: "I can't control myself". If the patient thinks his behaviour is observed by the dentist, it is possible that the dentist's response may subsequently initiate new thoughts, for example " T h e dentist thinks I am acting childish". Plausibly, the result of this interaction further decreases patient's confidence as being able to control his anxiety reactions. Thus, for the dentally anxious patient negative appraisal o f his own behaviour, including the belief o f not being able to stand pain, m a y increase anxiety, which interferes with treatment, and further reinforces the notion o f vulnerability and lack o f control. To this end, if treatment is to be effective, it seems most important to deal effectively with patients' tendency to think negatively and to diminish their catastrophic ideation, for example through some form o f cognitive therapy. The present results suggest that, irrespective o f the initial level o f anxiety, such therapeutic interventions should focus primarily on central beliefs and habitual negative self-statements, revolving a r o u n d issues o f losing control, embarrassment, the dentist, the condition o f the teeth, and possible negative consequences of treatment. In conclusion, the results o f the present study demonstrate that the D C Q is a sound measure for assessing negative beliefs and self-statements associated with dental treatment. Several researchers have asserted the importance o f such cognitive measures, for both assessment and evaluating treatment interventions (e.g. Kendall & Korgeski, 1979). In future investigations the D C Q m a y be useful as a measure to facilitate further study o f negative cognitions that are involved in the development, maintenance and exacerbation o f psychological distress in dentally anxious individuals. Although the present version of the D C Q appears to be a promising instrument, the utility o f the D C Q as an instrument sensitive to changes following psychological treatment, remains to be demonstrated. Overall, the current findings strengthen the view that diminishing catastrophizing ideation should be an important determinant o f adjustment to dental treatment and reduction o f psychological distress. A currently conducted study m a y throw some light on this and related issues.
REFERENCES Arntz, A., Lavy, E., van den Berg, G. & van Rijsoort, S. (1993). Negative beliefs of spider phobics: A psychometric evaluation of the spider phobia beliefs questionnaire. Advances in Behaviour Research and Therapy, 15, 257-277. Beck, A. T. (1976). Cognitive therapy and the emotional disorders. New York: International Universities Press. Beck, A. T., Emery, G. & Greenberg, R. L. (1985). Anxiety disorders and phobias: A cognitive perspective. New York: Basic Books. Beck, A. T., Laude, R. & Bohnert, M. (1974). Ideational components of anxiety neurosis. Archives of General Psychiatry, 3, 319-325. Cattell, R. B. (1978). The scientific use of factor analysis. New York: Plenum. Corah, N. L. (1969). Development of a dental anxiety scale. Journal of Dental Research, 48, 596. Corah, N. L., Gale, E. N. & lllig, S. J. (1978). Assessment of a dental anxiety scale. Journal of the American Dental Association, 97, 816 819. Domoto, P. K., Weinstein, P., Ohmura, M., Uchida, H. & Ohmachi, K. (1988). Results of a dental fear survey in Japan: Implications for dental public health in Asia. Community Dentistry and Oral Epidemiology, 16, 199-201. Eysenck, M. W. (1991). Cognitive factors in clinical psychology: Potential relevance to therapy. In Briley, M. & File, S. E. (Eds), New concepts in Anxiety. London: Macmillan. Foa, E. B., Steketee, G. & Rothbaum B. O. (1989). Behavioral/cognitive conceptualizations of post-traumatic stress disorder. Behavior Therapy, 20, 155-176. Hakeberg, M., Berggren, U. & Gr6ndahl, H.-G. (1993). A radiographic study of dental health in adult patients with dental anxiety. Community Dentistry and Oral Epidemiology, 21, 27-30. de Jongh, A. & Ter Horst, G. (1993). What do anxious patients think? An exploratory investigation of anxious dental patients' thoughts. Community Dentistry and Oral Epidemiology, 21, 221 223. de Jongh, A., Muris, P., Ter Horst, G. & Duyx, M. P. M. A. (1995). Acquisition and maintenance of dental anxiety: The role of conditioning experiences and cognitive factors. Behaviour Research and Therapy, 33, 205-210. de Jongh, A., Muris, P., Ter Horst, G., Van Zuuren, F. J. & De Wit, C. (1994). Cognitive correlates of dental anxiety. Journal of Dental Research, 73, 561-566. Kendall, P. C. & Korgeski, G. P. (1979). Assessment and cognitive-behavioral interventions. Cognitive Therapy and Research, 3, 1 21.
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Kent, G. & Gibbons, R. (1987). Self-etficacy and the control of anxious cognitions. Journal of Behaviour Therapy and Experimental Psychiatry, 18, 33-40. Koopmans, P. C., Sanderman, R., Timmerman, I. & Emmelkamp, P. M. G. (1994). The Irrational Beliefs Inventory (IBI): Development and psychometric evaluation. European Journal of Psychological Assessment, 10, 15--27. McGlynn, F. D., Gale, E. N., Glaros, A. G., LeResche, L., Massoth, D. L. & Weiffenbach, J. M. (1990). Biobehavioral research in dentistry: Some directions for the 1990s. Annals of Behavioral Medicine, 12, 133-140. Milgrom, P., Fiset, L., Melnick, S. & Weinstein, P. (1988). The prevalence and practice management consequences of dental fear in a major U.S. city. Journal of the American Dental Association, I16, 641~a47. van der Ploeg, J. W. P., Defares, P. B. & Spielberger, C. D. (1980). Handleiding bij de Zelfbeoordelings Vragenlijst. Lisse: Swets en Zeitlinger. Roy-Byrne, P., Milgrom, P., Khoon-Mei, T., Weinstein, P. & Katon, W. (1994). Psychopathology and psychiatric diagnosis in subjects with dental phobia. Journal of Anxiety Disorders, 8, 19-31. Schuurs, A., Duivenvoorden H., Thoden van Velzen, S. & Verhage, F. (1984). Dental anxiety, the parental family and regularity of dental attendance. Community Dentistry and Oral Epidemiology, 12, 95-98. Shafran, R., Booth, R. & Rachman, S. (1993). The reduction ofclaustrophobia--II: Cognitive analyses. Behaviour Research and Therapy, 31, 75--85. Spielberger, C. D., Gorsuch, R. L. & Lushene, R. E. (1970). Manual for the State-Trait Anxiety Inventory. Palo Alto, Calif.: Consulting Psychologists Press. Stouthard, M. & Hoogstraten, J. (1990). Prevalence of dental anxiety in the Netherlands. Community Dentistry and Oral Epidemiology, 18, 139-142. Steptoe, A. (1989). An abbreviated version of the Miller Behavioural Style Scale. British Journal of Clinical Psychology, 28, 183-184. Street, T., Craske, M. & Barlow, D. (1989). Sensations, cognitions and the perception of cues associated with expected and unexpected panic attacks. Behaviour Research and Therapy, 27, 189-198.
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NEGATIVE RELIABILITY
COGNITIONS AND
COGNITIONS
OF
DENTAL
VALIDITY
OF
THE
PHOBICS: DENTAL
QUESTIONNAIRE
A. D E J O N G H , 1. P. M U R I S , 2 N. S C H O E N M A K E R S I and G. T E R H O R S T l LDepartment of Social Dentistry and Dental Health Education, Academic Centre for Dentistry Amsterdam, Louwesweg 1, 1066 EA Amsterdam and 2Department of Experimental Abnormal Psychology, University of Limburg, P.O. Box 616, 6200 MD Maastricht, The Netherlands (Received 27 August 1994)
Summary--This study investigated the psychometric properties of the Dental Cognitions Questionnaire (DCQ). This measure contains 38 items and assesses both frequency and believability of negative cognitions related to dental treatment. The results indicated that the DCQ has good internal consistency, high test-retest reliability, and satisfactory concurrent validity, as indicated by positive associations with indices of anxiety and other cognitive measures (n = 180). Factor analysis revealed a one factor solution. Furthermore, the DCQ discriminated strongly between dental phobics (n = 85) and non-phobic Ss (n = 70). Moreover, it was found that combinations of DCQ items have substantially more explanatory power than did a measure of dental trait anxiety, explaining up to 70.7% of the variance in state anxiety ratings in the dental situation. Overall, it appears that dental phobics have many extremelynegativebeliefs and self-statements about themselves and about what might happen during treatment. Since certain cognitions seem to play a critical role in fear evocation, diminishing catastrophizing ideation may be an important determinant of adjustment to dental treatment and reduction of psychological distress.
INTRODUCTION The prevalence of dental anxiety and dental phobia in modern western societies is high. The results of research in North-American (e.g. Milgrom, Fiset, Melnick & Weinstein, 1988), Asian (e.g. Domoto, Weinstein, Melnick, Ohmura, Uchida & Ohmachi, 1988), and European populations (e.g. Schuurs, Duivenvoorden, Thoden van Velzen & Verhage, 1984; Stouthard & Hoogstraten, 1990) all indicate that about 40% of people are afraid to visit the dentist, 20% are highly anxious, whereas 5% are so anxious that dental treatment is avoided. Meanwhile, it is a well-established fact that dental anxiety and, in its wake, avoidance of dental treatment have detrimental effects on health (e.g. McGlynn, Gale, Glaros, LeResche, Massoth & Weiffenbach, 1990; Hakeberg, Berggren & Gr6ndahl, 1993). In recent years, both theorists and therapists have more and more advanced the idea that cognitive phenomena are important for the understanding of anxiety disorders (see e.g. Beck, 1976; Foa, Steketee & Rothbaum, 1989; Eysenck, 1992). According to Beck's (1976) cognitive model, emotional problems are accompanied by negative patterns in which individuals think about themselves and the external world. As far as anxiety and phobia in general are concerned, the negative patterns of thinking are centred around danger and harm (e.g. Beck, Laude & Bohnert, 1974). Support for the applicability of the cognitive approach to dental anxiety was provided by de Jongh and colleagues (de Jongh & Ter Horst, 1993; de Jongh, Muris, Ter Horst, Van Zuuren & de Wit, 1994; de Jongh, Muris, Ter Horst & Duyx, 1995). In these studies, it was found that dental anxiety is strongly associated with the tendency to experience negative or threatening thoughts. Although these findings make it difficult to tease out cause and effect, they suggest that negative thinking patterns play a crucial role in fear evocation. For example, while being treated a dental patient may think: "This dentist will drill in my tongue or cheek". If so, it is conceivable, that this person is apprehensive and difficult to treat. Moreover, it may be that this person will *Author for correspondence. 507
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not easily comply with techniques aimed at reducing anxiety reactions, such as relaxation or hypnosis. Anxiety level may even be heightened, if for instance, this person believes that relaxing makes him more vulnerable to the dentist's drill. Since it seems relatively easy to gather information about the occurrence of negative beliefs and self-statements (de Jongh & Ter Horst, 1993), this might be a useful way to gain understanding about the processes involved in maintenance of dental anxiety. Empirical evidence demonstrates that the occurrence of negative and catastrophic thoughts is not the only cognitive factor involved in dental anxiety. For example, the extent to which people believe to have control over their negative thoughts appears to be an equally important mediating factor. Kent and Gibbons (1987) found that highly anxious dental patients not only reported a greater number of negative thoughts, but also stronger efforts to control (i.e. to suppress) these thoughts as the appointment came closer in comparison with their low anxious counterparts. In a previous study (de Jongh et al., 1994), it was found that frequency of negative cognitions and degree of control, as indexed by questionnaires, together accounted for 75% of the variance in dental trait anxiety scores. Another seemingly likely, but yet unverified cognitive factor related to dental anxiety is the extent to which patients believe their negative cognitions. Plausibly, the patient who thinks that the dentist will drill in his cheek or tongue and perceives this event as most likely is more anxious than someone who thinks the prebability of such an event is low. Evidence for the contention that believability is associated with levels of anxiety has been derived from studies among people suffering from various types of anxieties. For example, spider phobics strongly believe various catastrophic and irrational ideas about spiders and encounters with spiders (Arntz, Lavy, van den Berg & van Rijsoort, 1993). In addition, Ss whose claustrophobia was reduced after therapy reported a significant reduction, not only in the number of negative thoughts but also in the believability of these thoughts (Shafran, Booth & Rachman, 1993). Thus, severity of dental anxiety may be associated with the degree of belief in negative cognitions. In order to better understand the cognitive characteristics of dental patients and their relationship with anxiety, research should aim at developing instruments that are specifically sensitive to assess the cognitive features seen as operative in the maintenance or exacerbation of dental anxiety. The aim of the present study was to examine the psychometric properties of such cognitive measure, the Dental Cognitions Questionnaire (DCQ), which was designed to assess frequency and believability of cognitions related to dental treatment. This questionnaire was constructed on the basis of the results of an earlier study exploring thought content among dentally anxious patients (De Jongh & Ter Horst, 1993), and studies examining differences in thought content between individuals high and low in dental anxiety (de Jongh et al., 1994; de Jongh et al., 1995; Kent & Gibbons, 1987). METHOD Subjects
For psychometric evaluation, the DCQ was applied to the following three S groups: (l) A university student group consisting of 180 first-year undergraduate students of the University of Amsterdam. As part of their study requirements, the Ss completed a large set of questionnaires, including the DCQ. Ss were excluded from the study if they never had been treated by a dentist (at least one filling). The number of remaining Ss was 151 (95 women, mean age = 21.9; 56 men, mean age = 24.4). They were regular dental patients, i.e. they indicated to comply with a schedule of dental check-ups every six months as is required by the Dutch national health insurance. (2) A group of dental phobics consisting of 85 patients (44 women) who awaited treatment in a dental fear clinic in Amsterdam. All patients had a history of avoiding dental treatment for several years (M = 8.5 years, SD = 9.0, range 1-34). Mean age of this group was 31.6 years (SD = 8.2, range 18-62). All patients were requested to complete various mailed questionnaires, including the DCQ. They were put on a waiting list as soon as the questionnaires had been returned to the clinic. A subsample of the phobic group participated in a study in which the effects of a cognitive
Negative cognitions of dental phobics
509
restructuring intervention were investigated. Since these patients had to rate their state anxiety in the dental situation, it was possible to assess the ability of the DCQ to predict state anxiety in the dental situation. In order to avoid confounding of treatment and occurrence of cognitions only the data of the patients (n = 31) who did not receive the cognitive intervention were used.* (3) A second group of first-year psychology students of the University of Amsterdam (n = 70; 58 women), who served as non-phobic control group for the dental phobics. The students had a mean age of 20.7 years (SD --- 2.2, range 18-28) and were all regular dental attenders (check-ups at least every six months). They received course credit points for the participation in the study.
Measures The Dental Cognitions Questionnaire (DCQ) consists of 38 negative cognitions (beliefs and self-statements) related to dental treatment. The first section of the questionnaire contains a list of 14 negative beliefs pertaining to dentistry in general (e.g. "Dentists don't care when it hurts") and to the patient himself (e.g. "I can't stand pain"). Following the sentence: "When knowing that I have to undergo dental treatment very soon, I think . . . " , Ss are asked to tick "Yes" or " N o " for each item. The second section consists of 24 negative self-statements that pertain to thinking during treatment (e.g. "Everything goes wrong"). Following the sentence: "While being treated, I t h i n k . . . " , Ss are again asked to tick "Yes" or " N o " for each item. In addition, Ss are instructed to rate the degree to which he/she believes each statement at that moment by filling in a percentage (0% = "I don't believe this thought at all" to 100% = "I am absolutely convinced that this thought is true"). "Yes"-responses on the items are summed to give a total negative cognition score (range 0-38). For each S, also a mean percentage believability score is computed. The following other measures were employed: The Dental Anxiety Scale (DAS; Corah, 1969) is a four-item self-report scale that has been widely used for measuring dental trait anxiety. Items are scored on a scale of 1 to 5 and summed to give an overall anxiety score ranging from 4 (not anxious at all) to 20 (extremely anxious). Cronbach's alpha of the DAS in the present sample was 0.95. The State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch & Lushene, 1970; van der Ploeg, Defares & Spielberger, 1980) consists of two separate self-report scales for measuring both trait anxiety and state anxiety. The STAI A-Trait scale (20-items) asks people to describe how they generally feel. The STAI A-State scale (20-items) requires people to describe how they feel at a particular moment in time. Cronbach's alpha's of the STAI scales in the present sample were both 0.92. The Irrational Beliefs Inventory (IBI; Koopmans, Sanderman, Timmerman & Emmelkamp, 1994) is a 50-item inventory measuring a wide range of irrational beliefs. The IBI consists of five subscales (problem avoidance, rigidity, worrying, need for approval and emotional irresponsibility). For the purpose of the present study only the worrying scale (12 items concerning worrying over possible misfortune and possible future accidents) was used. People are asked to indicate the extent to which they agree with each of the beliefs, from 1 (strongly disagree) to 5 (strongly agree). The score can be obtained by summation of the items. Cronbach's alpha of the scale in the present study was 0.87. State anxiety/tension was assessed with 100 mm visual analogue scales ranging from 0 (not at all anxious/tense) to 100 (very anxious/tense). Patients were asked to rate their anxiety upon arrival in the dentist's waiting room and while sitting in the dental chair. For dentist's rating of patient's anxiety also 100 mm visual analogue scales ranging from 0 (not at all anxious/tense) to 100 (very anxious/tense) were used.
Procedure Internal consistency, item-total correlation, and test-retest reliability were computed on the DCQ scores of the 180 students. The DCQ was administered two times with an interval of five weeks. Furthermore, to test concurrent validity, correlations between the DCQ and a number of other questionnaires, including the STAI, DAS, and IBI-worrying were calculated. *Initially this group consisted of 37 patients, but 6 patients were excluded because of missing data.
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Table I. Mean scores (and standard deviations) on the DCQ, DAS, STAI, and IBl-worrying including correlations between these measures for the student sample (n = 180)
STAI A-trait IBI-worrying DAS DCQ-frequency DCQ-believability Mean SD
STAI A-state
STAI A-trait
IBI-worrying
DAS
DCQ frequency
0.61" 0.55* 0.13 0.27* 0.23*
0.71" 0.26* 0.32* 0.31 *
0.28* 0.36* 0.22*
0.55* 0.36*
0.58*
8.6 2.9
9.8 6.9
35.8 10.0
38.2 9.8
33.3 8.7
DCQ believability
23.9 16.4
Note: *Significant at P < 0.05. STAI = Spielberger's State Trait Anxiety Inventory; IBI = Irrational Beliefs Inventory; DAS = Dental Anxiety Scale; DCQ = Dental Cognitions Questionnaire.
To assess discriminant validity DCQ scores of the dental phobics and the second group of students (non-phobic controls) were compared. The non-phobic Ss came in groups of 6 to an experimental room to complete the questionnaires. Predictive validity was examined by exploring the relationship between DCQ scores and dental state anxiety in a subsample of the phobic group. After filling out several questionnaires at home, including the DCQ, and a waiting period of at least one month these patients were phoned to make an appointment with one of the dentists. They were told that their first appointment only concerned a conversation about their dental anxiety and a check-up. At their visit to the dentist, in the waiting room of the dentist all patients were again asked to complete a set of questionnaires, including a visual analogue scale for ratings of state anxiety. Next, the patients were escorted to the dentist. During this first visit the dentist and the patient talked about patient's anxiety and then the dentist carried out a check-up. Before starting the check-up, while sitting in the dentist's chair, patients were asked to rate state anxiety again on a visual analogue scale. When the appointment was over, the dentist also rated patient's anxiety/tension. RESULTS
Reliability and dimensional structure Table 1 shows the means and standard deviations of the DCQ and the various other measures for the student group. An unpaired t-test showed that the frequency scores on the DCQ were significantly [t(149)=2.7, P <0.01] higher for women (M = 11.0; S D = 7.0) than for men (M = 7.9; SD = 6.4). No significant differences between the believability scores of women and men were found. Internal consistency was estimated by calculating Cronbach's alpha on the scores of the Ss at the first time they filled out the DCQ. The overall alphas for the full scale* were 0.89 for DCQ-frequency and 0.95 for DCQ-believability. The average item-total correlation for the scale was 0.45 with a range of r = 0.21, P < 0.01 (item 9) to r = 0.63, P < 0.001 (item 15). Test-retest reliability for the DCQ over a five week period in the non-anxious sample was evaluated using Pearson correlations and was 0.83. An exploratory principal component factor analysis with varimax rotation was performed on the DCQ items. A factor analysis performed on the frequency scores identified 13 factors with eigenvalues exceeding 1.0, together representing 65.9% of the variance. An exploratory factor analyses on the believability scores extracted seven factors with eigenvalues larger than !.0, which together accounted for 63.8% of the variance. However, inspection of the scree plots (Cattell, 1978) suggested a general one-factor model. Factor analyses performed on the data of men and women separately indicated similar patterns of results. Concurrent validity The relation between DCQ and STAI, DAS, and IBI-worrying were assessed using Pearson correlation coefficient (see Table 1). All measures were found to be significantly correlated, the only exception being the correlation between DAS and STAI-Trait (r = 0.13, P > 0.05). The correlation * B o t h sections (beliefs a n d self-statements) were r e g a r d e d as o n e scale since the s u m scores o f b o t h sections w e r e significantly c o r r e l a t e d ( f r e q u e n c y r = 0.65, P < 0.001 a n d believability r = 0.74, P < 0.001).
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between the frequency and believability scores of the DCQ was significant (r = 0.58, P < 0.001). Results revealed an acceptable level of validity. The magnitude of the correlations between the two DCQ subscales and a measure of dental trait anxiety (DAS) were both higher than the correlations between DCQ and measures of general trait anxiety or state anxiety. In addition, the correlations between DCQ and the worrying scale of the IBI were rather modest. These findings suggest that the DCQ taps unique (cognitive) aspects of anxiety related to the dental setting and not just trait anxiety or worrying about future events in general.
Discriminant validity Evidence for discriminant validity was derived by comparing DCQ scores of phobic and non-phobic persons. The questionnaire data were subjected to a series of 2 (sex: men/women) x 2 (group: phobic/non-phobic) analyses of variance (ANOVAs). An ANOVA performed on the DAS scores revealed a main effect of group [F(1,151)= 237.5, P < 0.001], indicating that, as expected, the phobic Ss had significantly higher dental trait anxiety scores (M = 17.6; SD = 2.2) than their non-phobic counterparts (M = 9.6; SD = 3.2). As for the DCQ frequency scores, the ANOVA also revealed a main effect of group [F(1,151) = 101.2, P < 0.001], indicating that the mean number of reported cognitions was significantly higher in the phobics (M = 22.5; SD = 6.7) than in the non-phobic controls (M = 10.0; SD = 7.0). The same was true for the mean believability rating (M = 50.1; SD = 16.3 vs M = 19.4; SD = 11.7), [F(1,151) = 130.6, P < 0.001]. No significant main effects of sex or interactions of group with sex were found. Since phobic and non-phobic groups differed significantly with respect to age the 2 × 2 ANOVAs were conducted again, this time only using age-matched groups (Ss between 18-24 years). A comparison of these groups essentially revealed the same pattern of results: phobic and non-phobic Ss scored significantly different on dental trait anxiety (DAS) [F(1,69)= 66.9, P < 0.001], frequency of cognitions [F(1,69)= 47.5, P < 0.001], and believability of cognitions [F(1,69) = 75.0, P < 0.001]. Again, no main effects of sex, nor interactions of sex with group were found. To determine which items contribute to the differences found in total DCQ scores, additional analyses were carried out. First of all, chi-square analyses were performed to compare the proportions of Ss in the phobic and non-phobic group who reported each of the 38 cognitions. In addition, a series of independent t-tests was computed comparing both groups with respect to mean believability of the cognitions. Bonferroni correction for multiple tests yielded a significance level of 0.0013 when an overall level of 0.05 was employed. All items, with proportions, means and standard deviations, are presented in Table 2. As can be seen, most cognitions were found to discriminate between both groups when the Bonferroni corrected level was employed. All but four items were more frequently endorsed by the phobic than by the non-phobic group, while for all items believability was found to be significantly higher in the phobic group than in the non-phobic group. In both groups item 16 ("This treatment will hurt") was most often reported (87.1% in the non-phobic group and 96.5% in the phobic group) and most strongly believed (mean believability in the non-phobic group 53.6% vs 83.6% in the phobic group). In the phobic group item 5 ("Dentists are often incapable") was least often reported (12.9%), while in the non-phobic group item 28 ( ' I will die during treatment") was least often indicated. Regarding the latter item, 14.1% of the phobic group patients indicated that this thought may occur to them during treatment, while in the non-phobic group only 1.4% of the patients indicated that during treatment this thought may pop into their head. In both groups the believability of this item was lowest (mean believability: 1.4% in the non-phobic group vs 18.2% in the phobic group).
Predictive validity To assess predictive validity the degree of relationship between patients' DCQ frequency scores and state anxiety ratings in the dental situation was assessed. The following three measures of state anxiety were used: self-reported anxiety in the waiting room, self-reported anxiety in the dental chair, and anxiety as rated by the dentist. First, the inter-relationships between the various ratings of patient's anxiety were computed. Dentists' ratings of patients' level of anxiety during the first meeting was found to be significantly (r = 0.48, P < 0.05) related to patients' self report of anxiety in the dental chair, but not with their
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Table 2. Proportions of subjects who reported DCQ cognitions and means (standard deviations) of DCQ-believability scores, for phobic and non-phobic patients. P values pertaining to group differences are given Non-phobic group (n = 70)
Phobic group (n = 85)
Frequency %
Believability M (SD)
Frequency %
Believability m (SD)
P Frequency
P Believability
30.0 21.4 21.4 14.3 18.6 28.6 20.0 17.1 8.6 24.3 50.0 28.6 25.7 7.1
31.7 (27.0) 19.7 (19.1) 16.2(17.1) 15.9 (18.7) I 0.3 (12.4) 21.4 (20.0) 18.4 (I 5.7) 10.1 (16.9) 6.6 (14.6) 22.4 (28.8) 39.4 (30.8) 27.3 (26.5) 21.9 (26.7) 7.8 (14.1)
60.0 70.6 48.2 64.7 12.9 78.8 41. I 62.4 61.2 68.2 71.8 69.4 62.4 16.5
45.2 (34.8) 47.8 (28.8) 37.8 (30.2) 45.0 (29.4) 19.5 (28.5) 59.5 (32.1) 35.0 (32.5) 53.3 (39.1) 57.1 (40.4) 64.9 (36.6) 68.5 (34.3) 60.0 (33.3) 54.0 (36.9) 14.7 (28.7)
0.001 0.001 0.001 0.001 0.460* 0.001 0.008 0.001 0.001 0.001 0.009 0.001 0.001 0.130"
0.005 0.001 0.001 0.00 I 0.007 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.034
17.1 87. I 17. I 32.9 27. I 38.6 11.4 15.7 24.3 58.6
9.7 (16.7) 53.6 (28.9) 14.6 (20.5) 19.2 (23.1) 24.1 (29.2) 25.1 (27.9) 12.4 (17.5) 13.9 (21.2) 14.1 (20.3) 39.0 (29.9)
45.9 96.5 54.1 63.5 78.8 80.0 63.5 56.8 71.8 92.9
39.4 (35.7) 83.6 (25.2) 48.6 (38.0) 49.4 (36.0) 70.3 (33.4) 71.0 (34.8) 60.3 (36.3) 53.8 (39.1) 52.1 (37.1) 80.2 (31.4)
0.001 0.062* 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001
0.001 0.001 0.00 I 0.00 I 0.001 0.001 0.001 0.001 0.001 0.001
27. I 67.1 44.3 1.4 17.1 5.7 7.1 55.7 37.1
18.2 (24.8) 40.6(30.2) 29.6 (30.0) 1.4(7.4) 14.4(23.0) 8.8 (17.5) 4.3 (10.8) 32.5 (30.1) 27.9 (26.2)
45.9 80.0 81.2 14.1 70.6 34.1 29.4 83.5 68.2
34.7 (35.5) 66.5(35.1) 78.4 (30.0) 18.2(34.9) 59.8(34.1) 31.3 (35.5) 25.1 (36.1) 62.1 (31.7) 58.8 (39.3)
0.026 0.102" 0.001 0.011 0.001 0.001 0.001 0.001 0.001
0.001 0.001 0.001 0.001 0.001 0.001 0.001 0,001 0,001
10.0 18.6 17.1 10.0
11.6 (16.1) 10.7 (15.9) 15.1 (19.6) 5.5 (10.2)
30.6 41.2 56.5 28.2
30.0 (36.1) 31.1 (32.9) 43.6 (38.2) 24.6 (29.9)
0.001 0.004 0.001 0.008
0,001 0.001 0.001 0,001
37.1
22.1 (26.1)
88.2
67.5 (34.3)
0.001
0,001
Beliefs about oneself and dentistry in general I. 2. 3. 4. 5. 6. 7. 8. 9. 10. II. 12. 13. 14.
Dentists do as they please Dentists are often impatient The dentist does not care if it hurts Dentists do not understand you Dentists are often incapable Dentists think you act childish Treatments often fail My teeth can't be saved I should be ashamed about my teeth My teeth might break I can't stand pain I am a tense person I am a difficult person l am someone with very long roots
Self-statements during treatment 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38.
Everything goes wrong This treatment will hurt My teeth will break Something surely will go wrong It never runs smoothly I am helpless I can't control myself l can't escape, I'm locked in Anaesthetics often do not work The sound of the drill frightens me The dentist will drill in my tongue, gums or cheek The nerve will be touched have no control over what happens will die during treatment will panic daring treatment will faint during treatment will suffocate during treatment can't stand this treatment for long will certainly have pain afterwards The filling will certainly fall out and has to be made again This treatment fails I become sick The dentist will lose control over his drill The dentist believes that I am a difficult patient and act childish
Note: Except items marked with * all Ps < 0.05.
anxiety ratings in the waiting room (r = 0.35, P > 0.05). Furthermore, between patients' selfreported level of state anxiety in the waiting room and in the dental chair a significant correlation was found (r = 0.50, P < 0.05). Next, it was determined which combination of DCQ items maximized the prediction of state anxiety in the dental situation. It was also examined whether dental trait anxiety could further improve the prediction of patients' state anxiety. Therefore, a series of separate stepwise multiple regression analyses were conducted with the scores on the DCQ items and dental trait anxiety being predictors, and the various state anxiety scores being dependent variables. To control for gender and the fact that a subsample of 14 patients had visited a dental hygienist,* these two variables were forced into the equations. It appeared that DCQ-items 16 ("This treatment will hurt") and 24 ("The sound of the drill frightens me") had no variance, since all patients indicated that these thoughts would occur during treatment. Consequently, the analyses were executed without these items. Table 3 shows the items that contributed significantly to the prediction of patients' anxiety in the dental situation. As can be seen, in only one case prediction of state anxiety could be significantly improved by the addition of dental trait anxiety score. A combination of three *The d e n t a l h y g i e n i s t d i d n o t t r e a t these patients, b u t p r o v i d e d t h e m o n l y with i n f o r m a t i o n a b o u t o r a l h e a l t h a n d p r e v e n t i v e behaviours.
Negative cognitions of dental phobics
513
cognitions significantly contributed to the prediction of state anxiety in the waiting room, explaining 61.9% of the total variance. With regard to self-reported anxiety in the dental chair a combination of five different DCQ items and the DAS score were entered into the equation. These variables together explained 70.7% of the variance in the criterion. As to the prediction of dentist's rating of patients' state anxiety, it was found that five different negative cognitions contributed significantly to the regression equation, explaining 70.4% of the variation in state anxiety ratings. The largest contribution was made by the belief "Dentists think you act childish".
DISCUSSION The current study examined reliability and validity of the DCQ, a self-report instrument designed to assess both occurrence and believability of negative cognitions related to dental treatment. The DCQ appeared to possess sufficient internal consistency, high test-retest reliability and demonstrated adequate concurrent validity, as judged by its correlations to other measures of either dental trait anxiety, general trait anxiety and worrying. Discriminant validity of the DCQ was supported by comparing the scores of phobic and non-phobic individuals. It was found that phobic patients not only reported a higher frequency of negative and catastrophic cognitions than non-phobic controls, they also showed a greater degree of believe in their negative thoughts. An inspection of the content of the thoughts of dental phobic individuals reveals that many thoughts pertain to ideas about suffocating or loss of control, and thus strongly resemble those held by panic patients (e.g. Street, Craske & Barlow, 1989), or individuals suffering from other type of phobias (e.g. Arntz et al., 1993; Shafran et al., 1993). This may be due to the fact that dental phobia is a diagnostically heterogeneous group. A recent study (Roy-Byrne, Milgrom, Khoon-Mei, Weinstein & Katon, 1994) indicated that 40% of a sample of phobic dental patients had a current diagnosis other than simple phobia. Thus, patients suffering from severe dental anxiety may in fact demonstrate characteristics of another anxiety disorder such as panic disorder. The present findings also provided evidence for predictive validity of the DCQ. It was found that a number of negative cognitions contributed significantly to the prediction of state anxiety in either waiting room (61.9%) or dental chair (70.7%). Such proportions of explained variance are remarkably high considering the fact that most patients filled out the DCQ more than one month before they visited the dentist. Combinations of specific negative beliefs and negative selfstatements appeared to have substantially more explanatory power than did the score of a situation specific measure of trait anxiety, the Dental Anxiety Scale (DAS). The fact that the prediction of anxiety in the dental situation could largely be explained by occurrence of particular combinations of negative cognitions strongly suggest that negative Table 3. Results of a series of stepwise regression analyses with patient's anxiety being the dependent variable (n = 31)*
df
F
Cumulative % variance
3, 27
8.6
43.3
4, 28 5, 25
9.1 10.4
51.9 61.9
Prediction of self-reported state anxiety in the dental chair I. "I am helpless" (20) 2. "'The dentist will drill in my tongue, gums or cheek" (25) 3. "'I can't control myself" (21) 4. "I can't stand pain" (11) 5. "Dentists think you act childish" (6) 6. DAS score
3, 4, 5, 6, 7, 8,
26 25 24 23 22 21
4.2 5.4 6.1 7.4 8.3 10.1
24.0 36.9 45.8 56.3 63.0 70.7
Prediction of state anxiety in the dental chair as rated by the dentist: I. "Dentists think you act childish" (6) 2. "I become sick" (36) 3. "Dentists are often impatient" (2) 4. "I can't stand pain" (1) 5. "It never runs smoothly" (19)
3, 4, 5, 6, 7,
26 25 24 23 22
8.5 10.1 10.2 10.5 10.8
43.8 55.6 61.4 66.2 70.4
Order of entry
Variable
Prediction of self-reported state anxiety in the waiting room: 1. " M y teeth might break" (10) 2. "The dentist believes that I am difficult patient and act childish" (38) 3. "'I become sick" (36)
Note: *After controlling for gender and appointment with dental hygienist.
514
A. de Jongh et al.
thinking patterns play a crucial role in fear evocation. The present findings, therefore, support Beck's notion that cognitions pertaining to the situation and their own resources have an effect on behaviour and result in increased psychological distress (e.g. Beck, 1976; Beck, Emery & Greenberg, 1985). In the dental situation, thoughts such as " I am helpless" may increase patients' sense o f vulnerability and heighten anxiety level. In turn, the dental patient may interpret his anxiety, and certain bodily sensations, as signs that he does not have control over himself and become in grip o f ideas such as: "I can't control myself". If the patient thinks his behaviour is observed by the dentist, it is possible that the dentist's response may subsequently initiate new thoughts, for example " T h e dentist thinks I am acting childish". Plausibly, the result of this interaction further decreases patient's confidence as being able to control his anxiety reactions. Thus, for the dentally anxious patient negative appraisal o f his own behaviour, including the belief o f not being able to stand pain, m a y increase anxiety, which interferes with treatment, and further reinforces the notion o f vulnerability and lack o f control. To this end, if treatment is to be effective, it seems most important to deal effectively with patients' tendency to think negatively and to diminish their catastrophic ideation, for example through some form o f cognitive therapy. The present results suggest that, irrespective o f the initial level o f anxiety, such therapeutic interventions should focus primarily on central beliefs and habitual negative self-statements, revolving a r o u n d issues o f losing control, embarrassment, the dentist, the condition o f the teeth, and possible negative consequences of treatment. In conclusion, the results o f the present study demonstrate that the D C Q is a sound measure for assessing negative beliefs and self-statements associated with dental treatment. Several researchers have asserted the importance o f such cognitive measures, for both assessment and evaluating treatment interventions (e.g. Kendall & Korgeski, 1979). In future investigations the D C Q m a y be useful as a measure to facilitate further study o f negative cognitions that are involved in the development, maintenance and exacerbation o f psychological distress in dentally anxious individuals. Although the present version of the D C Q appears to be a promising instrument, the utility o f the D C Q as an instrument sensitive to changes following psychological treatment, remains to be demonstrated. Overall, the current findings strengthen the view that diminishing catastrophizing ideation should be an important determinant o f adjustment to dental treatment and reduction o f psychological distress. A currently conducted study m a y throw some light on this and related issues.
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