Original Article Self-Efficacy and Affect as Mediators Between Pain Dimensions and Emotional Symptoms and Functional Limitation in Women With Fibromyalgia Cecilia Pe~ nacoba Puente, PhD,* cija Gallardo, PhD,* Lilian Velasco Furlong, PhD,* Carmen E Margarita Cigar an M endez, PhD,* Dolores Bedmar Cruz, MD,† and C esar Fern andez-de-las-Pe~ nas, PhD‡ ---
-
From the *Department of Psychology, Universidad Rey Juan Carlos, Alcorc on, Madrid, Spain; †Service of Anesthesiology, Reanimation and Pain Treatment, Fuenlabrada University Hospital, Madrid, Spain; ‡ Department of Physical Therapy, Occupational Therapy, Rehabilitation and Physical Medicine, Universidad Rey Juan Carlos, Alcorc on, Madrid, Spain. Address correspondence to: Cecilia Pe~ nacoba Puente, PhD, Department of Psychology, Universidad Rey Juan Carlos, Avda de Atenas s/n 28922 Alcorc on, Madrid, Spain. E-mail: [email protected] Received December 4, 2012; Revised April 12, 2014; Accepted April 13, 2014. The authors have no competing interests to report. 1524-9042/$36.00 Ó 2015 by the American Society for Pain Management Nursing http://dx.doi.org/10.1016/ j.pmn.2014.04.005
ABSTRACT:
The aim of this study was to investigate the role of self-efficacy and affect as mediators of the relationship between pain and several fibromyalgia (FM) symptoms (functional limitation, depression, and anxiety). We evaluated 144 women with FM for self-reported pain (numerical pain scale), pressure pain sensitivity (pressure pain thresholds), functional limitation (Fibromyalgia Impact Questionnaire), self-efficacy (Chronic Pain Self-Efficacy Scale), depressionanxiety (Hospital Anxiety and Depression Scale), and positive-negative affect (Positive-Negative Affect Scale). Mediating analyses were conducted with ordinary least squares multiple regression analysis. The results demonstrated that self-reported pain and pressure pain sensitivity exhibited significant relationships with functional limitation, anxiety, depression, self-efficacy, and affect. Affect mediated the relationship between pressure pain sensitivity and anxiety, whereas selfefficacy was the mediating variable between self-reported pain and functional limitation and depression. Our results support a complex nature of pain in women presenting with FM, as cognitive and emotional variables have different mediator relationships between pain dimensions and functional and emotional outcomes in women with FM. Ó 2015 by the American Society for Pain Management Nursing
Pain Management Nursing, Vol 16, No 1 (February), 2015: pp 60-68
Self-Efficacy and Affect
BACKGROUND Fibromyalgia, Pain, Functional Limitation, Anxiety, and Depression Fibromyalgia (FM) is a musculoskeletal chronic pain disorder of unknown pathophysiology that mainly affects women. It is characterized by widespread pain, sleep disturbances, fatigue, tenderness, cognitive difficulties, and other somatic complaints. Despite pain being the characteristic symptom in an FM diagnosis, its high rate of comorbidities has resulted in new diagnosis criteria by the American College of Rheumatology (ACR; Wolfe, Clauw, & Fitzcharles, 2010), which introduces the associated symptomatology as an additional criterion for the diagnosis. Therefore, it is not surprising that many authors have looked into the relationships between pain and associated comorbidities, such as functional limitations, anxiety, and depression. Accordingly, patients consider that the widespread pain and intense fatigue they feel are responsible for their limitations or the disabilities they suffer in their daily lives (Rivera, 2012). H€auser, Brahler, Wolfe, and Henningsen (2014) pointed out that pain intensity is associated to perceived disability, and Markkula et al. (2011), in a 14-year follow-up study, revealed that symptoms associated with FM, including pain, strongly correlate with early retirement due to disability. The association between pain, anxiety, and depression has been extensively explored in previous literature on chronic pain, establishing a bidirectional relationship that explains the vicious circles of pain– anxiety/depression (Woo, 2012). In the case of FM, its unknown etiology and the possible existence of psychiatric etiologies make the relationship between pain– anxiety/depression controversial (Spaeth, 2013). Nevertheless, when Fishbain, Cutler, Rosomoff, and Rosomoff (1997) conducted a review of 191 studies, they found that anxiety and depression should be understood as a consequence, not as a cause of chronic pain. Self-Efficacy and Affect in FM Both transversal and longitudinal studies have suggested that self-efficacy is essential in explaining the process of pain and its effect on different areas (Pastor, Lled o, Pons, & L opez-Roig, 2012). Likewise, self-efficacy is considered a key factor affecting the results of programs that try to improve the quality of life for these patients (Van Liew, Brown, Cronan, & Bigatti, 2013). Regarding physical effects, self-efficacy is associated with higher activity and less disability (Lled o et al., 2010). In relation to the emotional impact, high self-efficacy shows positive effects on anxiety and
61
depression (Lled o et al., 2010; Velasco, Zautra, Pe~ nacoba, L opez-L opez, & Barjola, 2010). In regard to affect, negative emotional states seem to increase the symptomatology associated with FM, and these patients appear to have difficulty maintaining positive emotional states while feeling pain (Finan, Zautra, & Davis, 2009; Kamping, Bomba, Kanske, Diesch, & Flor, 2013). Although the majority of studies have analyzed the predictive role of self-efficacy and affect over certain health outcomes as well as regarding the effects of the intervention programs, there are also some studies that analyze the mediator role of these factors on pain, symptomatology, and associated functional limitation (B€ orsbo, Gerdle, & Peolsson, 2010; Mir o, Martınez, Sanchez, Prados, & Medina, 2011; Park & Sonty, 2010). Pain as a Multidimensional Concept Although pain is a subjective experience, the truth is that given the unknown etiology of FM, there is a major interest in analyzing how the different approaches to its measurement (e.g., evoked pain vs. clinical pain) correlate to one another and are influenced by the same psychological processes. Thus, there are several self-reported methods used to evaluate pain intensity (e.g., numerical pain scale [NPS]). Additionally, pain also is examined by using quantitative methods such as pressure pain thresholds (PPT; Graven-Nielsen & Arendt-Nielsen, 2010). Patients with FM present a higher sensitivity to pain when using various forms of painful stimulation, such as electrodermal, thermal, or pressure (Blumenstiel et al., 2011). Despite the relevance of this matter, little is known about the relationship between evoked and clinical pain reports. To our knowledge, there are few studies that have looked into this relationship systematically, and the few that have done so generally show little correlation between both types of pain (Geisser et al., 2007; Smith, Harris, & Clauw, 2011). Staud, Vierck, Robinson, and Price (2006) suggested that the joint effect of evoked pain and negative effect might explain the higher percentage of variance in clinical pain reports. Intervention studies in FM also can provide some useful information about the relationship between evoked and clinical pain. During follow-up in longitudinal treatment studies in FM, improvements in clinical pain scores were found not to be parallel to changes in evoked pain measures, which are not associated with the course of treatment or clinical improvement (Bernardy, F€ uber, K€ ollner, & H€auser, 2010; H€auser, Thieme, & Turk, 2010; Sarzi-Puttini et al., 2011). These results suggest a certain independence and dissociation between both pain dimensions.
62
Pe~ nacoba Puente et al.
Most of the studies that analyze the relationship between psychological processes (e.g., self-efficacy and affect) and pain, some of which already have been mentioned, do use subjective pain measures (clinical pain), asking patients directly about their pain experience (self-reported pain; intensity in most occasions) through numeric or visual analog scales. Less known is the relationship between these processes and evoked pain measures, such as pressure pain sensitivity. The purpose of this study was to assess the role of self-efficacy and affect (negative and positive) as mediators of the relationship between pain (self-reported pain and pressure pain sensitivity) on depression, anxiety, and functional limitation.
METHODS Participants The study included 144 women with FM with an average age of 50 years (SD ¼ 11). Average reported illness duration (time since diagnosis) was 18 years (SD ¼ 13). Of the women, 81% were married, 12.1% were single, 6% divorced, and the remaining 3% were widowed. Fifty-one percent had primary studies, 21% secondary education, 12% high school education, and the remaining 16% had no studies. Twenty-nine percent were working at the time of the study, 60% were not employed, and the remaining 11% were absent from work. Of the participants, 61% used analgesics, 65% used antidepressants, and 49% used other medication (e.g., anti-inflammatories, anxiolytics, and myorelaxants) to manage FM symptoms. Instruments and Variables Predictor Variables: Pain Dimensions. A Multidimensional Approach to the Assessment of FM Pain was Adopted, Consisting of the following Measures: 1. Self-reported pain was assessed with an NPS, ranging from 0 (no pain) to 10 (worst pain). The NPS has been shown to be valid and reliable in FM (Price, Patel, Robinson, & Staud, 2008). Patients were asked for their mean level of pain, the worst and the lowest level of generalized pain experienced in the preceding week. The mean score obtained from the three measures was used as a global pain score. 2. Pressure pain sensitivity was assessed by PPTs. PPT is defined as the minimal amount of pressure where a sensation of pressure first changes to pain (Vanderweeen, Oostendorp, Vaes, & Duquet, 1996). An electronic algometer (SomedicÓ, Farsta, Sweden) was used to measure PPT (kPa). The pressure was applied at a rate of 30 kPa/second. The mean score from three trials (intraexaminer reliability) was
calculated and used for the main analysis. A 30-second resting period was allowed between each trial. The reliability of pressure algometry has been found to be high (intraclass correlation [ICC], 0.91; 95% confidence interval [CI], 0.82-0.97) (Vanderweeen et al., 1996). In the current study, intraexaminer reliability ranged between 0.96 and 0.98. PPT levels were bilaterally assessed over the C5-C6 zygapophyseal joint, the second metacarpal, and the tibialis anterior muscle. The order of assessment was randomized among participants. To obtain representative data about pressure pain sensitivity, a mean value of PPT was obtained for each patient.
Mediating Variables. Pain Self-Efficacy was Assessed Using the Spanish Version (Martın-Arag on et al., 1999) of the Chronic Pain Self-Efficacy Scale (CPSS), a 22-Item Questionnaire Designed to Measure Chronic Pain patients’ Perceived Self-Efficacy to cope with the Consequences of Chronic Pain (Anderson, Dowds, Pelletz, Edwards, & Peeters-Asdourian, 1995). the CPSS Includes Three Factors: Self-Efficacy for Pain Management, Self-Efficacy for Coping with Symptoms, and Self-Efficacy for Physical Function. Positive and negative effects were assessed using the Spanish version (Sandın et al., 1999) of the Positive and Negative Affect Scale-PANAS (Watson, Clark, & Tellegen, 1988), a 20-item questionnaire that is composed of two factors: positive affect and negative affect (10 items for subscale). Criterion Variables. Functional Limitation was Assessed Using the first Subscale (Physical Scale) of the Spanish Version (Esteve, Rivera, Salvat, Gracia, & Alegre, 2007) of the Fibromyalgia Impact Questionnaire (FIQ; Burckhardt, Clark, & Bennett, 1991). the FIQ Physical Scale Consists of 10 Items Assessing how FM Symptoms affect Daily Function in a Typical Week, where Higher Scores Indicate a More Negative Effect. Anxiety and depression were assessed using the Spanish version (Herrero et al., 2003) of the Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983). The HADS is a 14-item self-report screening scale (7 items each for the anxiety and depression subscales) originally developed to indicate the possible presence of anxiety and depression in the setting of a medical nonpsychiatric outpatient clinic. Recently, Luciano, Barrada, Aguado, Osma, and Garcia-Campayo (2013) pointed out a bifactorial structure for HADS among FM patients. Sampling Procedures Women (ages $18) diagnosed with FM according to ACR criteria (Wolfe, Smythe, & Yunus, 1990) were recruited from the Fuenlabrada University Hospital,
Self-Efficacy and Affect
Madrid, Spain. Exclusion criteria included the existence of concomitant rheumatologic disorders, such as rheumatoid arthritis, systemic lupus erythematosus, Hashimoto’s disease, Sjogren’s syndrome, scleroderma, and reflex sympathetic dystrophy; and the existence of psychotic disorders, bipolar disorder, or other serious psychiatric conditions. According to the inclusion and exclusion criteria established, patients were informed of the study and, if the patient agreed to participate, informed consent was signed. Once signed, an experienced rheumatologist from the hospital’s pain unit, who was a member of the research team, confirmed the FM diagnosis by performing a physical tender point examination. The patient then was given an appointment at the fibromyalgia unit of Rey Juan Carlos University, Madrid, where a battery of tests was administered and a specialized physiotherapist performed the pressure pain sensitivity measure (algometry). Of the 175 patients who signed the informed consent, 160 completed the rest of the measures at the fibromyalgia unit, and 144 constituted valid registers. The study protocol was approved by local Ethics Committee and conducted following the Helsinki Declaration.
Statistical Analysis To test for the presence of mediating effects, we conducted an ordinary least squares multiple regression analysis (Baron & Kenny, 1986). Several preconditions must be met to assess whether a variable has a mediating effect, establishing: (a) significant correlations between the predictor variables (pain dimensions: self-reported pain and pressure pain sensitivity) and the mediator (affect and self-efficacy); (b) significant correlations between the predictor variables and the outcome variables (anxiety, depression, and functional limitation); and, (c) significant correlations between the mediator variables and outcome variables. These preconditions were assessed with Pearson’s correlations between the variables of interest. When the preconditions have been fulfilled, the final step consists of showing that the strength of the association between pain dimensions and outcome variables is significantly reduced when the mediating variable is added to the regression model. Partial mediation is demonstrated when the beta weight for the predictor variable is reduced (but not to nonsignificance) when the proposed mediator is added to the equation. Full mediation is demonstrated if the beta value for the predictor variable is reduced from significance to nonsignificance when the proposed mediator is added to the equation (Baron & Kenny, 1986).
63
Based on the observed correlations, we conducted hierarchical regression analyses. Because a reduced b weight in itself does not seem to be indicative of significance, we additionally performed the Sobel test to demonstrate partial mediation (Sobel, 1982). Additionally, the relationships between sociodemographic and clinical variables (age, marital status, education level, working, years of diagnosis, years of symptoms, and medication use) and the target variables were explored by conducting the appropriate test for each variable (Pearson’s correlations, t tests and one-way analysis of variances). Sociodemographic and clinical variables showing a significant relationship with the target variables were entered in step 1 of the hierarchical regression analyses.
RESULTS Preliminary Analysis: Correlations Among Variables As shown in Table 1, pressure pain sensitivity levels (PPT) showed negative correlations with anxiety and functional limitation. The NPS showed positive correlations with all the outcome variables (anxiety, depression, and functional limitation). In relation to the mediating factors (affect and self-efficacy), PPT levels exhibited a negative correlation with negative affect and a positive correlation with positive affect. Selfreported pain revealed negative correlations with self-efficacy dimensions. Depression and functional limitation also correlated with affect and self-efficacy, whereas anxiety also exhibited some other correlations: positive with negative affect and negative with self-efficacy for coping with symptoms. The possible effect of sociodemographic and clinical variables (age, marital status, education level, working, years of diagnosis, years of symptoms, and medication use) on outcomes was examined, with no significant relationships. Test of Model 1 (Pain/Self-Efficacy/FM Outcomes) This model evaluated whether self-efficacy would mediate the relationship between pain (self-reported pain and pressure pain sensitivity) and anxiety, depression, and functional limitation. Taking pressure pain sensitivity as a predictive factor, we found that in association to the preconditions, none of the dimensions of self-efficacy significantly correlates to the predictive pressure pain sensitivity (Table 1), therefore the precondition (a) is not fulfilled, which implies the impossibility of mediation of self-
64
Pe~ nacoba Puente et al.
TABLE 1. Correlations Among Variables Variables
Mean (SD)
2
3
4
5
1. PPT 142.72 (65.57) –.200 .341* .332* .213 2. NPS (0-10) 6.82 (1.17) 409† 305† .277* 3. FIQ 13.06 (6.24) (.88) .060 .240* 4. Anxiety 19.76 (3.56) (.78) .582† 5. Depression 17.78 (3.13) (.72) 6. Positive affect 26.09 (7.74) 7. Negative affect 26.76 (8.35) 8. Self-efficacy 30.87 (14.51) physical functioning 9. Self-efficacy 36.42 (15.84) symptoms 10. Self-efficacy pain 16.44 (11.10)
6
7
.279* .412 .109 .216 .243* .250* .211 .339† .331† .296† (.89) .528† (.88) †
8
9
10
.050 .403† .604† .157 .327† .319† .328† (.88)
.144 .296* .376† .259* .317† .477† .439† .694†
.153 .307† .375† .105 .263* .337† .215* .701†
(.87)
.699† (.86)
PPT ¼ pressure pain thresholds; NPS ¼ numerical pain scale; FIQ ¼ Fibromyalgia Impact Questionnaire. The coefficient a for each scale is presented along the diagonal. *p < .05. † p < .01.
efficacy in the relationship between PPT and anxiety, depression, and functional limitation. Taking self-reported pain as the predictive variable, we observed that after the fulfillment of the preconditions (Table 1), we can consider the following mediations: (a) the mediating factor is self-efficacy for coping with symptoms and the result variables are functional limitation, anxiety, and depression; (b) the mediating factor is self-efficacy for physical function and the result outcomes are functional limitation and depression; (c) the mediating factor is self-efficacy for pain control and the result variables are functional limitation and depression. Once the possible mediations of model 1 had been tested (Table 2), self-efficacy for physical function
completely mediated the relationship between selfreported pain and depression, and between selfreported pain and functional limitation. Self-efficacy for pain management mediated the relationships between self-reported pain and depression (completely) and self-efficacy for coping with symptoms mediated the relationships between self-reported pain and functional limitation (partially, Sobel test z ¼ 2.01, p ¼ .04).
Test of Model 2 (Pain/Affect/FM Outcomes) The second model examined whether affect (positive and negative) mediates the relationship among pain (self-reported pain and pressure pain sensitivity) and anxiety, depression, and functional limitation.
TABLE 2. Mediation Model Pain-Self-efficacy-FM outcomes FM Outcomes Functional limitation (FIQ) Step 1: NPS Step 2: Self-efficacy physical function Step 1: NPS Step 2: Self-efficacy physical function Depression Step 1: NPS Step 2: Self-efficacy physical function Step 1: NPS Step 2: Self-efficacy pain
F
R2
11.722‡ 16.348‡ 10.789‡ 7.396‡
0.145 0.328 0.149 0.186
6.544† 6.175‡ 5.644† 5.310‡
0.084 0.150 0.068 0.119
IncR2
0.183 0.037 0.066 0.051
Beta
t
0.399 (0.150)* 0.502 0.405 (0.318*)* 0.242
3.424‡ 4.219‡ 3.285‡ 1.874†
0.291(0.179)* 0.279 0.287(0.210)* 0.264
2.558† 2.324† 2.376† 2.156†
FIQ ¼ Fibromyalgia Impact Questionnaire; NPS ¼ numerical pain scale Standardized regression coefficients (betas) are derived from the step in which they were added to the equation. *Beta value after introduction of mediating variable. Significant Beta weight comparisons in Step 2 using Sobel’s test are presented in bold. † p < .05; ‡p < .01
65
Self-Efficacy and Affect
TABLE 3. Mediation Model Pain–Affect–FM Outcomes FM Outcomes
F
R2
IncR2
b
t
Anxiety Step 1: PPT Step 2: Negative affect
5.959† 23.756‡
0.110 0.508
0.398
0.332 (0.026)* 0.701
2.441† 6.158‡
PPT ¼ pressure pain thresholds. Standardized regression coefficients (b) are derived from the step in which they were added to the equation. *b value after introduction of mediating variable. † p < .05. ‡ p < .01.
Taking self-reported pain as the predictive variable, we observed that considering the preconditions, self-reported pain maintains no significant correlation with positive nor with negative effect (precondition (a); Table 1), which implies the impossibility of mediation of positive and negative affect in the relationship between self-reported pain and anxiety, depression, and functional limitation. Taking pressure pain sensitivity as the predictive variable, we observed that after the fulfillment of the preconditions (Table 1), we can consider the following mediations: (1) the mediating factor is the positive affect and the result outcome is functional limitation; (2) the mediating factor is the negative affect and the result outcomes are functional limitation or anxiety. Once the possible mediations of model 2 had been tested (Table 3), the analyses revealed that negative affect mediated the relationship between PPT and anxiety, and the mediation effect was total.
DISCUSSION The scores found for anxiety and depression, pain self-efficacy, and self-reported pain in our sample are similar to those found in other similar Spanish studies about FM (Martın-Arag on et al., 2001; Moioli & Merayo, 2005; Vallejo, Rivera, Esteve-Vives, & Rodrıguez-Mu~ noz, 2012), although there was a greater variability in functional limitation and affect, thus, supporting the representativeness of the sample regarding symptomatology. The results of our study show that self-reported pain and pressure pain sensitivity are valid pain indicators in FM, independent from one another, as was shown in the small amount of previous studies on the subject (Laursen, Bajaj, Olesen, Delmar, & ArendtNielsen, 2005; Smith et al., 2011). Also, our results suggest that both self-efficacy and affect have a mediating role among pain and functional limitation, anxiety, and depression, as has also been pointed out in
previous literature (B€ orsbo et al., 2010; Mir o et al., 2011). Despite this, as noted earlier, most of the literature that has analyzed the roles of self-efficacy and affect have used self-reported pain measures, and to our knowledge there aren’t any studies that have analyzed the different roles that these variables have on the various results of FM, depending on what pain indicator is being considered (self-reported pain and evoked pain measures). Because of this, our results should be considered very relevant. An interesting finding of the current study has been that both pain indicators were related to different cognitive-emotional variables. Thus, although pressure pain sensitivity only presented a significant correlation with affect; self-reported pain correlated with self-efficacy, therefore supporting different pain mechanisms. Both pain dimensions were related to outcomes variables. As expected, we found significant relationships between pressure pain sensitivity (negative) and self-reported pain (positive) with anxiety and functional limitation, but only self-reported pain had a significant relationship with depression. These results are consistent with previous studies conducted on FM where higher levels of pain were associated with greater functional limitation (H€auser et al., 2014; Markkula et al., 2011), and higher anxiety and depression (Spaeth, 2013), although it should be noted that the majority of these studies were conducted using self-reported pain measures. The few studies that have used pressure pain sensitivity as the predictive variable showed that pressure pain hypersensitivity also is related to impairment in quality of life (Laursen et al., 2005). Our results suggest that within the comorbidity associated to FM (functional limitation, anxiety, and depression), depression seems to be a consequence associated with the self-informed pain measures, but not with pressure pain sensitivity measures. As previously noted, the connection between pain and pain self-efficacy has been reported
66
Pe~ nacoba Puente et al.
previously, particularly in the context of FM (Pastor et al., 2012), which is in accordance with our results, where self-reported pain was related to all selfefficacy dimensions. This demonstrates that selfefficacy is a key variable in the results of intervention programs that try to improve quality of life for these patients (Bernardy et al., 2010). Nevertheless, it should be noted that the majority of the studies used selfreported pain and not pressure pain sensitivity measures. The absence of a relationship between pressure pain sensitivity and self-efficacy, which has not been studied frequently in previous literature, could possibly help to explain the fact that cognitivebehavioral therapy and multidisciplinary programs, centered on increasing self-efficacy, are not very effective in modifying ‘‘objective’’ pain variables, whereas at the same time they show robust effect sizes in reducing sleep problems, depression, and functional status (Bernardy et al., 2010; Glombiewski et al., 2010). We also found that self-efficacy mediated the relationship between self-reported pain and depression as well as functional limitation, as presented in other studies (B€ orsbo et al., 2010; Mir o et al., 2011). Because not all self-efficacy dimensions behave in the same way, in view of the results, self-efficacy for physical function plays an important mediating role between pain and functional limitation and depression, whereas selfefficacy for pain management only would be related to functional limitation. We found a mediating effect of negative effect between pain sensitivity and anxiety, which suggests that negative effect seems to be a key variable for understanding anxiety associated with pain sensitivity in FM. Despite the significant relationships between PPT and positive effect, there was an absence of results supporting positive effect as a mediator between pressure pain sensitivity and anxiety. It is possible that positive effect, in accordance with what Finan et al. (2009) reported, can play a role associated to other health results, but possibly not regarding pressure pain sensitivity. Likewise, future studies should focus on the possible modulator role of positive effect, in line with the differential studies between moderation and modulation in chronic pain by Schiaffmo and Revenson (1992). In this context, the limited mediator role of effect in relation to the important mediator role of selfefficacy should be noted. This detail is in line with the small amount of attention that affect has received as a mediator variable in chronic pain literature, especially if we take into account that the only relationship mediated by negative affect is the one between pressure pain sensitivity and anxiety. We could possibly interpret this mediation of negative affect as an
amplifier of the vicious circles involving pain and anxiety, which have been thoroughly documented in previous literature (Woo, 2012). It is also important to emphasize the relative independence of anxiety and depression in relation to the different predictive dimensions of pain implicated and to the psychological processes involved; although anxiety relates more to affective variables (negative affect) and physical indicators of pain (PPT), depression is associated with cognitive variables (self-efficacy) and pain perception (NPS). We should take into account the potential limitations of the current study. First, the convenient nature of the sample, composed of voluntary women with FM recruited from a hospital, prevents the generalization of our findings to the general FM population. Nevertheless, considering the problems associated with a correct FM diagnosis (Wolfe et al., 2010), the fact that the sample was derived from a single hospital, increases the validity of the diagnosis. Second, the current findings were based on cross-sectional data, and future studies should use longitudinal designs to further provide evidence of potential causal relationships. Finally, in relation to the important relationship between self-efficacy and functional limitations, it would be interesting to include limitation measures, such as observational measures, that are not only self-report measures. Furthermore, the first 10 items of the FIQ scale used in this study ask the patient to report on his or her perceived capacity of specific activities. This could raise doubts over a possible superposition of the measures of functional limitation and self-efficacy. The obtained results have important clinical implications. Mainly that it would be important to adjust multidisciplinary programs, which include mostly cognitive-behavioral therapy (CBT). As we have pointed out, previous literature has suggested that when reviewing different intervention programs, whether multidisciplinary programs or those based on CBT, pain is still the least successful indicator of improvement (Bernardy et al., 2010; Glombiewski et al., 2010; H€auser et al., 2010). Our results suggest the complexity of the pain experience, and the different roles psychological processes play (selfefficacy and affect) for different indicators of pain (self-reported pain and pressure pain sensitivity). Taking this into consideration, it would seem that it is necessary to follow a more complex model for pain assessment, taking into account that the psychological processes (e.g., effect and self-esteem) that we manipulate using CBT, maintain different relationships between the different dimensions of pain. To have better knowledge about these relationships has important practical implications for health services provision for people diagnosed with FM, so as to be
Self-Efficacy and Affect
able to adapt treatment to the variables that we aim to modify and to be able to personalize treatments, given the vast clinical variability among patients with FM (Rehm et al., 2010).
67
A better knowledge of these relationships and an integral approach would improve the quality of life of these patients, as they are mostly dissatisfied with their current treatments.
REFERENCES Anderson, K. O., Dowds, B. N., Pelletz, R. E., Edwards, W. T., & Peeters-Asdourian, C. (1995). Development and initial validation of a scale to measure self-efficacy beliefs in patients with chronic pain. Pain, 63, 77–84. Baron, R. M., & Kenny, D. A. (1986). The moderatormediator variable distinction in social psychological research: Conceptual, strategic and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182. Bernardy, K., F€ uber, N., K€ ollner, V., & H€auser, W. (2010). Efficacy of cognitive-behavioral therapies in fibromyalgia syndrome. A systematic review and meta-analysis of randomized controlled trials. Journal of Rheumatology, 37, 1991–2205. Blumenstiel, K., Gerhardt, A., Rolke, R., Bieber, C., Tesarz, J., Friederich, H. C., Eich, W., & Treede, R. D. (2011). Quantitative sensory testing profiles in chronic back pain are distinct from those in fibromyalgia. Clinical Journal of Pain, 27(8), 682–690. B€ orsbo, B., Gerdle, B., & Peolsson, M. (2010). Impact of the interaction between self-efficacy, symptoms and catastrophising on disability, quality of life and health in with chronic pain patients. Disability and Rehabilitation, 32, 1387–1396. Burckhardt, C. S., Clark, S. R., & Bennett, R. M. (1991). The fibromyalgia impact Questionnaire: Development and validation. Journal of Rheumatology, 18, 728–733. Esteve, J., Rivera, J., Salvat, I., Gracia, M., & Alegre, C. (2007). Propuesta de una versi on de consenso del Fibromyalgia Impact Questionnaire (FIQ) para la poblaci on espa~ nola. Reumatologıa Clınica, 3, 21–24. Finan, P. H., Zautra, A. J., & Davis, M. C. (2009). Daily affect relations in fibromyalgia patients reveal positive affective disturbance. Psychosomatic Medicine, 71(4), 474–482. Fishbain, D., Cutler, R., Rosomoff, H., & Rosomoff, R. (1997). Chronic pain associated depression: Antecedent or consequence of chronic pain? a review. Clinical Journal of Pain, 13, 116–137. Geisser, M. E., Gracely, R. H., Giesecke, T., Petzke, F. W., Williams, D. A., & Clauw, D. J. (2007). The association between experimental and clinical pain measures among persons with fibromyalgia and chronic fatigue syndrome. European Journal of Pain, 11, 202–207. Glombiewski, J. A., Sawyer, A. T., Gutermann, J., Koenig, K., Rief, W., & Hofmann, S. G. (2010). Psychological trearments for fibromyalgia: A meta-analysis. Pain, 151(2), 280–295. Graven-Nielsen, T., & Arendt-Nielsen, L. (2010). Assessment of mechanisms in localized and widespread musculoskeletal pain. Nature Reviews Rheumatology, 6, 599–606. H€auser, W., Brahler, E., Wolfe, F., & Henningsen, P. (2014). Patient health questionnaire 15 as a generic measure of severity in fibromyalgia syndrome: Surveys with patients of three different settings. Journal of Psychosomatic Research, 76(4), 307–311.
H€auser, W., Thieme, K., & Turk, D. C. (2010). Guidelines on the management of fibromyalgia syndrome: A systematic review. European Journal of Pain, 14, 5–10. Herrero, M. J., Blanch, J., Pei, J. M., De Pablo, J., Pintor, L., & Bulbena, A. (2003). A validation study of the hospital anxiety and depression scale (HADS) in a Spanish population. General Hospital Psychiatry, 25, 277–283. Kamping, S., Bomba, I. C., Kanske, P., Diesch, E., & Flor, H. (2013). Deficient modulation of pain by a positive emotional context in fibromyalgia patients. Pain, 154, 1846–1855. Laursen, B. S., Bajaj, P., Olesen, A. S., Delmar, C., & Arendt-Nielsen, L. (2005). Health related quality of life and quantitative pain measurement in females with chronic nonmalignant pain. European Journal of Pain, 9, 267–275. Lled o, A., Pastor, M. A., Pons, N., L opez-Roig, S., RodrıguezMarın, J., & Bruehl, S. (2010). Control beliefs, coping and emotions: Exploring relationships to explain Fibromyalgia health outcomes. International Journal of Clinical and Health Psychology, 10, 459–476. Luciano, J. V., Barrada, J. R., Aguado, J., Osma, J., & GarciaCampayo, J. (2013). Bifactor analysis and construct validity of the HADS: A cross-sectional and longitudinal study in fibromyalgia patients. Psychological Assessment, 26, 395–406. Markkula, R., Kalso, E., Huunan-Seppala, A., Koskenvuo, M., Koskenvuo, K., Leino-Arjas, P., & Kaprio, J. (2011). The burden of symptoms predicts early retirement: A twin cohort study on fibromyalgia-associated symptoms. European Journal of Pain, 15, 741–747. Martın-Arag on, M., Pastor, M. A., Lled o, A., Terol, M. C., Rodrıguez Marın, J., & L opez Roig, S. (2001). Percepci on de control en el sındrome fibromialgico. Psicothema, 13, 568– 591. Martın-Arag on, M., Pastor, M. A., Rodrıguez-Marın, J., March, M. J., Lled o, A., & L opez-Roig, S. (1999). Percepci on de auto-eficacia en dolor cr onico: Adaptaci on y validaci on de la Chronic Pain Self-Efficacy Scale. Revista de Psicologıa de la Salud, 11, 53–76. Mir o, E., Martınez, M. P., Sanchez, A. I., Prados, G., & Medina, A. (2011). When is pain related to emotional distress and daily functioning in fibromyalgia syndrome? the mediating roles of self-efficacy and sleep quality. British Journal Health Psychology, 16, 799–814. Moioli, B., & Merayo, L. A. (2005). Effects of psychological intervention on pain and emotional state of persons with fibromyalgia. Revista de la Sociedad Espa~ nola del Dolor, 12, 476–484. Park, S. H., & Sonty, N. (2010). Positive affect mediates the relationship between pain-related coping efficacy and interference in social functioning. Journal of Pain, 11, 1267– 1273. Pastor, M. A., Lled o, A., Pons, N., & L opez-Roig, S. (2012). Dolor y fibromialgia. Aportaciones desde la Psicologıa. In C. Pe~ nacoba (Ed.), Fibromialgia y promoci on de la salud. Herramientas de intervenci on psicosocial (pp. 77–122). Madrid: Dykinson.
68
Pe~ nacoba Puente et al.
Price, D. D., Patel, R., Robinson, M. E., & Staud, R. (2008). Characteristics of electronic visual analogue and numerical scales for ratings of experimental pain in healthy subjects and fibromyalgia patients. Pain, 140(1), 158–166. http:// www.sciencedirect.com/science/help/doi.htm. Rehm, S. E., Koroschetz, J., Gockel, U., Brosz, M., Freynhagen, R., T€ olle, T. R., & Baron, R. (2010). A crosssectional survey of 3035 patients with fibromyalgia: Subgroups of patients with typical comorbidities and sensory symptom profiles. Rheumatology, 49(6), 1146–1152. Rivera, J. (2012). La fibromialgia en el sistema sanitario espa~ nol. Generalidades e Impacto en la calidad de vida. In C. Pe~ nacoba (Ed.), Fibromialgia y promoci on de la salud. Herramientas de intervenci on psicosocial (pp. 45–73). Madrid: Dykinson. Sandın, B., Charot, P., Lostao, L., Joiner, T. E., Santed, M. A., & Valiente, R. M. (1999). Escala PANAS de afecto positivo y negativo: Validaci on Factorial y convergencia transcultural. Psicothema, 11, 37–51. Sarzi-Puttini, P., Atzeni, F., Salaffi, F., Cazzola, M., Benucci, M., & Mease, P. J. (2011). Multidisciplinary approach to fibromyalgia: What is the teaching? Best Practice & Research. Clinical Rheumatology, 25, 311–319. Schiaffmo, K. M., & Revenson, T. A. (1992). The role of perceived self-efficacy, perceived control, and causal attributions in adaptation to rheumatoid arthritis: Distinguishing mediator from moderator effects. Personality and Social Psychology Bulletin, 18(6), 709–718. Smith, H. S., Harris, R., & Clauw, D. (2011). Fibromyalgia: An afferent processing disorder leading to a complex pain generalized syndrome. Pain Physician, 14, E217–E245. Sobel, M. E. (1982). Asymptotic intervals for indirect effects in structural equations models. In S. Leinhart (Ed.), Sociological methodology (pp. 290–312). San Francisco: Jossey-Bass. Spaeth, M. (2013). Fibromyalgia syndrome review. Journal of Musculoskeletal Pain, 21(2), 178–182. Staud, R., Vierck, C. J., Robinson, M. E., & Price, D. D. (2006). Overall fibromyalgia pain is predicted by ratings
of local pain and pain-related negative affect. Possible role of peripheral tissues. Rheumatology, 45, 1409–1415. Vallejo, M. A., Rivera, J., Esteve-Vives, J., & RodrıguezMu~ noz, M. F. (2012). Uso del cuestionario Hospital Anxiety and Depression Scale (HADS) para evaluar la ansiedad y la depresi on en pacientes con fibromialgia. Revista de Psiquiatrıa y Salud Mental, 5, 107–114. Van Liew, C., Brown, K. C., Cronan, T. A., & Bigatti, S. M. (2013). The effects of self-efficacy on depression and pain in fibromyalgia syndrome: Does initial depression matter? Journal of Musculoskeletal Pain, 21(2), 113–125. Vanderweeen, L., Oostendorp, R. B., Vaes, P., & Duquet, W. (1996). Pressure algometry in manual therapy. Manual Therapy, 1, 258–265. Velasco, L., Zautra, A., Pe~ nacoba, C., L opez-L opez, A., & Barjola, P. (2010). Cognitive-affective assets and vulnerabilities: Two factors influencing adaptation to fibromyalgia. Psychology and Health, 25, 197–212. Watson, D., Clark, L. A., & Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: The PANAS scales. Journal of Personality Social Psychology, 54, 1063–1070. Wolfe, F., Clauw, D. J., & Fitzcharles, M. A. (2010). The American College of Rheumatology Preliminary Diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care and Research, 62, 600–610. Wolfe, F., Smythe, H. A., & Yunus, M. B. (1990). The American College of Rheumatology 1990 criteria for classification of fibromyalgia: Report of the multicentre criteria committee. Arthritis Rheumatology, 33, 160–172. Woo, K. Y. (2012). Chronic wound-associated pain, psychological stress, and wound healing. Surgical Technology International, 22, 57–65. Zigmond, A. S., & Snaith, R. P. (1983). The hospital anxiety and depression scale. Acta Psychiatric Scandinavian, 67, 361–370.
-
From the *Department of Psychology, Universidad Rey Juan Carlos, Alcorc on, Madrid, Spain; †Service of Anesthesiology, Reanimation and Pain Treatment, Fuenlabrada University Hospital, Madrid, Spain; ‡ Department of Physical Therapy, Occupational Therapy, Rehabilitation and Physical Medicine, Universidad Rey Juan Carlos, Alcorc on, Madrid, Spain. Address correspondence to: Cecilia Pe~ nacoba Puente, PhD, Department of Psychology, Universidad Rey Juan Carlos, Avda de Atenas s/n 28922 Alcorc on, Madrid, Spain. E-mail: [email protected] Received December 4, 2012; Revised April 12, 2014; Accepted April 13, 2014. The authors have no competing interests to report. 1524-9042/$36.00 Ó 2015 by the American Society for Pain Management Nursing http://dx.doi.org/10.1016/ j.pmn.2014.04.005
ABSTRACT:
The aim of this study was to investigate the role of self-efficacy and affect as mediators of the relationship between pain and several fibromyalgia (FM) symptoms (functional limitation, depression, and anxiety). We evaluated 144 women with FM for self-reported pain (numerical pain scale), pressure pain sensitivity (pressure pain thresholds), functional limitation (Fibromyalgia Impact Questionnaire), self-efficacy (Chronic Pain Self-Efficacy Scale), depressionanxiety (Hospital Anxiety and Depression Scale), and positive-negative affect (Positive-Negative Affect Scale). Mediating analyses were conducted with ordinary least squares multiple regression analysis. The results demonstrated that self-reported pain and pressure pain sensitivity exhibited significant relationships with functional limitation, anxiety, depression, self-efficacy, and affect. Affect mediated the relationship between pressure pain sensitivity and anxiety, whereas selfefficacy was the mediating variable between self-reported pain and functional limitation and depression. Our results support a complex nature of pain in women presenting with FM, as cognitive and emotional variables have different mediator relationships between pain dimensions and functional and emotional outcomes in women with FM. Ó 2015 by the American Society for Pain Management Nursing
Pain Management Nursing, Vol 16, No 1 (February), 2015: pp 60-68
Self-Efficacy and Affect
BACKGROUND Fibromyalgia, Pain, Functional Limitation, Anxiety, and Depression Fibromyalgia (FM) is a musculoskeletal chronic pain disorder of unknown pathophysiology that mainly affects women. It is characterized by widespread pain, sleep disturbances, fatigue, tenderness, cognitive difficulties, and other somatic complaints. Despite pain being the characteristic symptom in an FM diagnosis, its high rate of comorbidities has resulted in new diagnosis criteria by the American College of Rheumatology (ACR; Wolfe, Clauw, & Fitzcharles, 2010), which introduces the associated symptomatology as an additional criterion for the diagnosis. Therefore, it is not surprising that many authors have looked into the relationships between pain and associated comorbidities, such as functional limitations, anxiety, and depression. Accordingly, patients consider that the widespread pain and intense fatigue they feel are responsible for their limitations or the disabilities they suffer in their daily lives (Rivera, 2012). H€auser, Brahler, Wolfe, and Henningsen (2014) pointed out that pain intensity is associated to perceived disability, and Markkula et al. (2011), in a 14-year follow-up study, revealed that symptoms associated with FM, including pain, strongly correlate with early retirement due to disability. The association between pain, anxiety, and depression has been extensively explored in previous literature on chronic pain, establishing a bidirectional relationship that explains the vicious circles of pain– anxiety/depression (Woo, 2012). In the case of FM, its unknown etiology and the possible existence of psychiatric etiologies make the relationship between pain– anxiety/depression controversial (Spaeth, 2013). Nevertheless, when Fishbain, Cutler, Rosomoff, and Rosomoff (1997) conducted a review of 191 studies, they found that anxiety and depression should be understood as a consequence, not as a cause of chronic pain. Self-Efficacy and Affect in FM Both transversal and longitudinal studies have suggested that self-efficacy is essential in explaining the process of pain and its effect on different areas (Pastor, Lled o, Pons, & L opez-Roig, 2012). Likewise, self-efficacy is considered a key factor affecting the results of programs that try to improve the quality of life for these patients (Van Liew, Brown, Cronan, & Bigatti, 2013). Regarding physical effects, self-efficacy is associated with higher activity and less disability (Lled o et al., 2010). In relation to the emotional impact, high self-efficacy shows positive effects on anxiety and
61
depression (Lled o et al., 2010; Velasco, Zautra, Pe~ nacoba, L opez-L opez, & Barjola, 2010). In regard to affect, negative emotional states seem to increase the symptomatology associated with FM, and these patients appear to have difficulty maintaining positive emotional states while feeling pain (Finan, Zautra, & Davis, 2009; Kamping, Bomba, Kanske, Diesch, & Flor, 2013). Although the majority of studies have analyzed the predictive role of self-efficacy and affect over certain health outcomes as well as regarding the effects of the intervention programs, there are also some studies that analyze the mediator role of these factors on pain, symptomatology, and associated functional limitation (B€ orsbo, Gerdle, & Peolsson, 2010; Mir o, Martınez, Sanchez, Prados, & Medina, 2011; Park & Sonty, 2010). Pain as a Multidimensional Concept Although pain is a subjective experience, the truth is that given the unknown etiology of FM, there is a major interest in analyzing how the different approaches to its measurement (e.g., evoked pain vs. clinical pain) correlate to one another and are influenced by the same psychological processes. Thus, there are several self-reported methods used to evaluate pain intensity (e.g., numerical pain scale [NPS]). Additionally, pain also is examined by using quantitative methods such as pressure pain thresholds (PPT; Graven-Nielsen & Arendt-Nielsen, 2010). Patients with FM present a higher sensitivity to pain when using various forms of painful stimulation, such as electrodermal, thermal, or pressure (Blumenstiel et al., 2011). Despite the relevance of this matter, little is known about the relationship between evoked and clinical pain reports. To our knowledge, there are few studies that have looked into this relationship systematically, and the few that have done so generally show little correlation between both types of pain (Geisser et al., 2007; Smith, Harris, & Clauw, 2011). Staud, Vierck, Robinson, and Price (2006) suggested that the joint effect of evoked pain and negative effect might explain the higher percentage of variance in clinical pain reports. Intervention studies in FM also can provide some useful information about the relationship between evoked and clinical pain. During follow-up in longitudinal treatment studies in FM, improvements in clinical pain scores were found not to be parallel to changes in evoked pain measures, which are not associated with the course of treatment or clinical improvement (Bernardy, F€ uber, K€ ollner, & H€auser, 2010; H€auser, Thieme, & Turk, 2010; Sarzi-Puttini et al., 2011). These results suggest a certain independence and dissociation between both pain dimensions.
62
Pe~ nacoba Puente et al.
Most of the studies that analyze the relationship between psychological processes (e.g., self-efficacy and affect) and pain, some of which already have been mentioned, do use subjective pain measures (clinical pain), asking patients directly about their pain experience (self-reported pain; intensity in most occasions) through numeric or visual analog scales. Less known is the relationship between these processes and evoked pain measures, such as pressure pain sensitivity. The purpose of this study was to assess the role of self-efficacy and affect (negative and positive) as mediators of the relationship between pain (self-reported pain and pressure pain sensitivity) on depression, anxiety, and functional limitation.
METHODS Participants The study included 144 women with FM with an average age of 50 years (SD ¼ 11). Average reported illness duration (time since diagnosis) was 18 years (SD ¼ 13). Of the women, 81% were married, 12.1% were single, 6% divorced, and the remaining 3% were widowed. Fifty-one percent had primary studies, 21% secondary education, 12% high school education, and the remaining 16% had no studies. Twenty-nine percent were working at the time of the study, 60% were not employed, and the remaining 11% were absent from work. Of the participants, 61% used analgesics, 65% used antidepressants, and 49% used other medication (e.g., anti-inflammatories, anxiolytics, and myorelaxants) to manage FM symptoms. Instruments and Variables Predictor Variables: Pain Dimensions. A Multidimensional Approach to the Assessment of FM Pain was Adopted, Consisting of the following Measures: 1. Self-reported pain was assessed with an NPS, ranging from 0 (no pain) to 10 (worst pain). The NPS has been shown to be valid and reliable in FM (Price, Patel, Robinson, & Staud, 2008). Patients were asked for their mean level of pain, the worst and the lowest level of generalized pain experienced in the preceding week. The mean score obtained from the three measures was used as a global pain score. 2. Pressure pain sensitivity was assessed by PPTs. PPT is defined as the minimal amount of pressure where a sensation of pressure first changes to pain (Vanderweeen, Oostendorp, Vaes, & Duquet, 1996). An electronic algometer (SomedicÓ, Farsta, Sweden) was used to measure PPT (kPa). The pressure was applied at a rate of 30 kPa/second. The mean score from three trials (intraexaminer reliability) was
calculated and used for the main analysis. A 30-second resting period was allowed between each trial. The reliability of pressure algometry has been found to be high (intraclass correlation [ICC], 0.91; 95% confidence interval [CI], 0.82-0.97) (Vanderweeen et al., 1996). In the current study, intraexaminer reliability ranged between 0.96 and 0.98. PPT levels were bilaterally assessed over the C5-C6 zygapophyseal joint, the second metacarpal, and the tibialis anterior muscle. The order of assessment was randomized among participants. To obtain representative data about pressure pain sensitivity, a mean value of PPT was obtained for each patient.
Mediating Variables. Pain Self-Efficacy was Assessed Using the Spanish Version (Martın-Arag on et al., 1999) of the Chronic Pain Self-Efficacy Scale (CPSS), a 22-Item Questionnaire Designed to Measure Chronic Pain patients’ Perceived Self-Efficacy to cope with the Consequences of Chronic Pain (Anderson, Dowds, Pelletz, Edwards, & Peeters-Asdourian, 1995). the CPSS Includes Three Factors: Self-Efficacy for Pain Management, Self-Efficacy for Coping with Symptoms, and Self-Efficacy for Physical Function. Positive and negative effects were assessed using the Spanish version (Sandın et al., 1999) of the Positive and Negative Affect Scale-PANAS (Watson, Clark, & Tellegen, 1988), a 20-item questionnaire that is composed of two factors: positive affect and negative affect (10 items for subscale). Criterion Variables. Functional Limitation was Assessed Using the first Subscale (Physical Scale) of the Spanish Version (Esteve, Rivera, Salvat, Gracia, & Alegre, 2007) of the Fibromyalgia Impact Questionnaire (FIQ; Burckhardt, Clark, & Bennett, 1991). the FIQ Physical Scale Consists of 10 Items Assessing how FM Symptoms affect Daily Function in a Typical Week, where Higher Scores Indicate a More Negative Effect. Anxiety and depression were assessed using the Spanish version (Herrero et al., 2003) of the Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983). The HADS is a 14-item self-report screening scale (7 items each for the anxiety and depression subscales) originally developed to indicate the possible presence of anxiety and depression in the setting of a medical nonpsychiatric outpatient clinic. Recently, Luciano, Barrada, Aguado, Osma, and Garcia-Campayo (2013) pointed out a bifactorial structure for HADS among FM patients. Sampling Procedures Women (ages $18) diagnosed with FM according to ACR criteria (Wolfe, Smythe, & Yunus, 1990) were recruited from the Fuenlabrada University Hospital,
Self-Efficacy and Affect
Madrid, Spain. Exclusion criteria included the existence of concomitant rheumatologic disorders, such as rheumatoid arthritis, systemic lupus erythematosus, Hashimoto’s disease, Sjogren’s syndrome, scleroderma, and reflex sympathetic dystrophy; and the existence of psychotic disorders, bipolar disorder, or other serious psychiatric conditions. According to the inclusion and exclusion criteria established, patients were informed of the study and, if the patient agreed to participate, informed consent was signed. Once signed, an experienced rheumatologist from the hospital’s pain unit, who was a member of the research team, confirmed the FM diagnosis by performing a physical tender point examination. The patient then was given an appointment at the fibromyalgia unit of Rey Juan Carlos University, Madrid, where a battery of tests was administered and a specialized physiotherapist performed the pressure pain sensitivity measure (algometry). Of the 175 patients who signed the informed consent, 160 completed the rest of the measures at the fibromyalgia unit, and 144 constituted valid registers. The study protocol was approved by local Ethics Committee and conducted following the Helsinki Declaration.
Statistical Analysis To test for the presence of mediating effects, we conducted an ordinary least squares multiple regression analysis (Baron & Kenny, 1986). Several preconditions must be met to assess whether a variable has a mediating effect, establishing: (a) significant correlations between the predictor variables (pain dimensions: self-reported pain and pressure pain sensitivity) and the mediator (affect and self-efficacy); (b) significant correlations between the predictor variables and the outcome variables (anxiety, depression, and functional limitation); and, (c) significant correlations between the mediator variables and outcome variables. These preconditions were assessed with Pearson’s correlations between the variables of interest. When the preconditions have been fulfilled, the final step consists of showing that the strength of the association between pain dimensions and outcome variables is significantly reduced when the mediating variable is added to the regression model. Partial mediation is demonstrated when the beta weight for the predictor variable is reduced (but not to nonsignificance) when the proposed mediator is added to the equation. Full mediation is demonstrated if the beta value for the predictor variable is reduced from significance to nonsignificance when the proposed mediator is added to the equation (Baron & Kenny, 1986).
63
Based on the observed correlations, we conducted hierarchical regression analyses. Because a reduced b weight in itself does not seem to be indicative of significance, we additionally performed the Sobel test to demonstrate partial mediation (Sobel, 1982). Additionally, the relationships between sociodemographic and clinical variables (age, marital status, education level, working, years of diagnosis, years of symptoms, and medication use) and the target variables were explored by conducting the appropriate test for each variable (Pearson’s correlations, t tests and one-way analysis of variances). Sociodemographic and clinical variables showing a significant relationship with the target variables were entered in step 1 of the hierarchical regression analyses.
RESULTS Preliminary Analysis: Correlations Among Variables As shown in Table 1, pressure pain sensitivity levels (PPT) showed negative correlations with anxiety and functional limitation. The NPS showed positive correlations with all the outcome variables (anxiety, depression, and functional limitation). In relation to the mediating factors (affect and self-efficacy), PPT levels exhibited a negative correlation with negative affect and a positive correlation with positive affect. Selfreported pain revealed negative correlations with self-efficacy dimensions. Depression and functional limitation also correlated with affect and self-efficacy, whereas anxiety also exhibited some other correlations: positive with negative affect and negative with self-efficacy for coping with symptoms. The possible effect of sociodemographic and clinical variables (age, marital status, education level, working, years of diagnosis, years of symptoms, and medication use) on outcomes was examined, with no significant relationships. Test of Model 1 (Pain/Self-Efficacy/FM Outcomes) This model evaluated whether self-efficacy would mediate the relationship between pain (self-reported pain and pressure pain sensitivity) and anxiety, depression, and functional limitation. Taking pressure pain sensitivity as a predictive factor, we found that in association to the preconditions, none of the dimensions of self-efficacy significantly correlates to the predictive pressure pain sensitivity (Table 1), therefore the precondition (a) is not fulfilled, which implies the impossibility of mediation of self-
64
Pe~ nacoba Puente et al.
TABLE 1. Correlations Among Variables Variables
Mean (SD)
2
3
4
5
1. PPT 142.72 (65.57) –.200 .341* .332* .213 2. NPS (0-10) 6.82 (1.17) 409† 305† .277* 3. FIQ 13.06 (6.24) (.88) .060 .240* 4. Anxiety 19.76 (3.56) (.78) .582† 5. Depression 17.78 (3.13) (.72) 6. Positive affect 26.09 (7.74) 7. Negative affect 26.76 (8.35) 8. Self-efficacy 30.87 (14.51) physical functioning 9. Self-efficacy 36.42 (15.84) symptoms 10. Self-efficacy pain 16.44 (11.10)
6
7
.279* .412 .109 .216 .243* .250* .211 .339† .331† .296† (.89) .528† (.88) †
8
9
10
.050 .403† .604† .157 .327† .319† .328† (.88)
.144 .296* .376† .259* .317† .477† .439† .694†
.153 .307† .375† .105 .263* .337† .215* .701†
(.87)
.699† (.86)
PPT ¼ pressure pain thresholds; NPS ¼ numerical pain scale; FIQ ¼ Fibromyalgia Impact Questionnaire. The coefficient a for each scale is presented along the diagonal. *p < .05. † p < .01.
efficacy in the relationship between PPT and anxiety, depression, and functional limitation. Taking self-reported pain as the predictive variable, we observed that after the fulfillment of the preconditions (Table 1), we can consider the following mediations: (a) the mediating factor is self-efficacy for coping with symptoms and the result variables are functional limitation, anxiety, and depression; (b) the mediating factor is self-efficacy for physical function and the result outcomes are functional limitation and depression; (c) the mediating factor is self-efficacy for pain control and the result variables are functional limitation and depression. Once the possible mediations of model 1 had been tested (Table 2), self-efficacy for physical function
completely mediated the relationship between selfreported pain and depression, and between selfreported pain and functional limitation. Self-efficacy for pain management mediated the relationships between self-reported pain and depression (completely) and self-efficacy for coping with symptoms mediated the relationships between self-reported pain and functional limitation (partially, Sobel test z ¼ 2.01, p ¼ .04).
Test of Model 2 (Pain/Affect/FM Outcomes) The second model examined whether affect (positive and negative) mediates the relationship among pain (self-reported pain and pressure pain sensitivity) and anxiety, depression, and functional limitation.
TABLE 2. Mediation Model Pain-Self-efficacy-FM outcomes FM Outcomes Functional limitation (FIQ) Step 1: NPS Step 2: Self-efficacy physical function Step 1: NPS Step 2: Self-efficacy physical function Depression Step 1: NPS Step 2: Self-efficacy physical function Step 1: NPS Step 2: Self-efficacy pain
F
R2
11.722‡ 16.348‡ 10.789‡ 7.396‡
0.145 0.328 0.149 0.186
6.544† 6.175‡ 5.644† 5.310‡
0.084 0.150 0.068 0.119
IncR2
0.183 0.037 0.066 0.051
Beta
t
0.399 (0.150)* 0.502 0.405 (0.318*)* 0.242
3.424‡ 4.219‡ 3.285‡ 1.874†
0.291(0.179)* 0.279 0.287(0.210)* 0.264
2.558† 2.324† 2.376† 2.156†
FIQ ¼ Fibromyalgia Impact Questionnaire; NPS ¼ numerical pain scale Standardized regression coefficients (betas) are derived from the step in which they were added to the equation. *Beta value after introduction of mediating variable. Significant Beta weight comparisons in Step 2 using Sobel’s test are presented in bold. † p < .05; ‡p < .01
65
Self-Efficacy and Affect
TABLE 3. Mediation Model Pain–Affect–FM Outcomes FM Outcomes
F
R2
IncR2
b
t
Anxiety Step 1: PPT Step 2: Negative affect
5.959† 23.756‡
0.110 0.508
0.398
0.332 (0.026)* 0.701
2.441† 6.158‡
PPT ¼ pressure pain thresholds. Standardized regression coefficients (b) are derived from the step in which they were added to the equation. *b value after introduction of mediating variable. † p < .05. ‡ p < .01.
Taking self-reported pain as the predictive variable, we observed that considering the preconditions, self-reported pain maintains no significant correlation with positive nor with negative effect (precondition (a); Table 1), which implies the impossibility of mediation of positive and negative affect in the relationship between self-reported pain and anxiety, depression, and functional limitation. Taking pressure pain sensitivity as the predictive variable, we observed that after the fulfillment of the preconditions (Table 1), we can consider the following mediations: (1) the mediating factor is the positive affect and the result outcome is functional limitation; (2) the mediating factor is the negative affect and the result outcomes are functional limitation or anxiety. Once the possible mediations of model 2 had been tested (Table 3), the analyses revealed that negative affect mediated the relationship between PPT and anxiety, and the mediation effect was total.
DISCUSSION The scores found for anxiety and depression, pain self-efficacy, and self-reported pain in our sample are similar to those found in other similar Spanish studies about FM (Martın-Arag on et al., 2001; Moioli & Merayo, 2005; Vallejo, Rivera, Esteve-Vives, & Rodrıguez-Mu~ noz, 2012), although there was a greater variability in functional limitation and affect, thus, supporting the representativeness of the sample regarding symptomatology. The results of our study show that self-reported pain and pressure pain sensitivity are valid pain indicators in FM, independent from one another, as was shown in the small amount of previous studies on the subject (Laursen, Bajaj, Olesen, Delmar, & ArendtNielsen, 2005; Smith et al., 2011). Also, our results suggest that both self-efficacy and affect have a mediating role among pain and functional limitation, anxiety, and depression, as has also been pointed out in
previous literature (B€ orsbo et al., 2010; Mir o et al., 2011). Despite this, as noted earlier, most of the literature that has analyzed the roles of self-efficacy and affect have used self-reported pain measures, and to our knowledge there aren’t any studies that have analyzed the different roles that these variables have on the various results of FM, depending on what pain indicator is being considered (self-reported pain and evoked pain measures). Because of this, our results should be considered very relevant. An interesting finding of the current study has been that both pain indicators were related to different cognitive-emotional variables. Thus, although pressure pain sensitivity only presented a significant correlation with affect; self-reported pain correlated with self-efficacy, therefore supporting different pain mechanisms. Both pain dimensions were related to outcomes variables. As expected, we found significant relationships between pressure pain sensitivity (negative) and self-reported pain (positive) with anxiety and functional limitation, but only self-reported pain had a significant relationship with depression. These results are consistent with previous studies conducted on FM where higher levels of pain were associated with greater functional limitation (H€auser et al., 2014; Markkula et al., 2011), and higher anxiety and depression (Spaeth, 2013), although it should be noted that the majority of these studies were conducted using self-reported pain measures. The few studies that have used pressure pain sensitivity as the predictive variable showed that pressure pain hypersensitivity also is related to impairment in quality of life (Laursen et al., 2005). Our results suggest that within the comorbidity associated to FM (functional limitation, anxiety, and depression), depression seems to be a consequence associated with the self-informed pain measures, but not with pressure pain sensitivity measures. As previously noted, the connection between pain and pain self-efficacy has been reported
66
Pe~ nacoba Puente et al.
previously, particularly in the context of FM (Pastor et al., 2012), which is in accordance with our results, where self-reported pain was related to all selfefficacy dimensions. This demonstrates that selfefficacy is a key variable in the results of intervention programs that try to improve quality of life for these patients (Bernardy et al., 2010). Nevertheless, it should be noted that the majority of the studies used selfreported pain and not pressure pain sensitivity measures. The absence of a relationship between pressure pain sensitivity and self-efficacy, which has not been studied frequently in previous literature, could possibly help to explain the fact that cognitivebehavioral therapy and multidisciplinary programs, centered on increasing self-efficacy, are not very effective in modifying ‘‘objective’’ pain variables, whereas at the same time they show robust effect sizes in reducing sleep problems, depression, and functional status (Bernardy et al., 2010; Glombiewski et al., 2010). We also found that self-efficacy mediated the relationship between self-reported pain and depression as well as functional limitation, as presented in other studies (B€ orsbo et al., 2010; Mir o et al., 2011). Because not all self-efficacy dimensions behave in the same way, in view of the results, self-efficacy for physical function plays an important mediating role between pain and functional limitation and depression, whereas selfefficacy for pain management only would be related to functional limitation. We found a mediating effect of negative effect between pain sensitivity and anxiety, which suggests that negative effect seems to be a key variable for understanding anxiety associated with pain sensitivity in FM. Despite the significant relationships between PPT and positive effect, there was an absence of results supporting positive effect as a mediator between pressure pain sensitivity and anxiety. It is possible that positive effect, in accordance with what Finan et al. (2009) reported, can play a role associated to other health results, but possibly not regarding pressure pain sensitivity. Likewise, future studies should focus on the possible modulator role of positive effect, in line with the differential studies between moderation and modulation in chronic pain by Schiaffmo and Revenson (1992). In this context, the limited mediator role of effect in relation to the important mediator role of selfefficacy should be noted. This detail is in line with the small amount of attention that affect has received as a mediator variable in chronic pain literature, especially if we take into account that the only relationship mediated by negative affect is the one between pressure pain sensitivity and anxiety. We could possibly interpret this mediation of negative affect as an
amplifier of the vicious circles involving pain and anxiety, which have been thoroughly documented in previous literature (Woo, 2012). It is also important to emphasize the relative independence of anxiety and depression in relation to the different predictive dimensions of pain implicated and to the psychological processes involved; although anxiety relates more to affective variables (negative affect) and physical indicators of pain (PPT), depression is associated with cognitive variables (self-efficacy) and pain perception (NPS). We should take into account the potential limitations of the current study. First, the convenient nature of the sample, composed of voluntary women with FM recruited from a hospital, prevents the generalization of our findings to the general FM population. Nevertheless, considering the problems associated with a correct FM diagnosis (Wolfe et al., 2010), the fact that the sample was derived from a single hospital, increases the validity of the diagnosis. Second, the current findings were based on cross-sectional data, and future studies should use longitudinal designs to further provide evidence of potential causal relationships. Finally, in relation to the important relationship between self-efficacy and functional limitations, it would be interesting to include limitation measures, such as observational measures, that are not only self-report measures. Furthermore, the first 10 items of the FIQ scale used in this study ask the patient to report on his or her perceived capacity of specific activities. This could raise doubts over a possible superposition of the measures of functional limitation and self-efficacy. The obtained results have important clinical implications. Mainly that it would be important to adjust multidisciplinary programs, which include mostly cognitive-behavioral therapy (CBT). As we have pointed out, previous literature has suggested that when reviewing different intervention programs, whether multidisciplinary programs or those based on CBT, pain is still the least successful indicator of improvement (Bernardy et al., 2010; Glombiewski et al., 2010; H€auser et al., 2010). Our results suggest the complexity of the pain experience, and the different roles psychological processes play (selfefficacy and affect) for different indicators of pain (self-reported pain and pressure pain sensitivity). Taking this into consideration, it would seem that it is necessary to follow a more complex model for pain assessment, taking into account that the psychological processes (e.g., effect and self-esteem) that we manipulate using CBT, maintain different relationships between the different dimensions of pain. To have better knowledge about these relationships has important practical implications for health services provision for people diagnosed with FM, so as to be
Self-Efficacy and Affect
able to adapt treatment to the variables that we aim to modify and to be able to personalize treatments, given the vast clinical variability among patients with FM (Rehm et al., 2010).
67
A better knowledge of these relationships and an integral approach would improve the quality of life of these patients, as they are mostly dissatisfied with their current treatments.
REFERENCES Anderson, K. O., Dowds, B. N., Pelletz, R. E., Edwards, W. T., & Peeters-Asdourian, C. (1995). Development and initial validation of a scale to measure self-efficacy beliefs in patients with chronic pain. Pain, 63, 77–84. Baron, R. M., & Kenny, D. A. (1986). The moderatormediator variable distinction in social psychological research: Conceptual, strategic and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182. Bernardy, K., F€ uber, N., K€ ollner, V., & H€auser, W. (2010). Efficacy of cognitive-behavioral therapies in fibromyalgia syndrome. A systematic review and meta-analysis of randomized controlled trials. Journal of Rheumatology, 37, 1991–2205. Blumenstiel, K., Gerhardt, A., Rolke, R., Bieber, C., Tesarz, J., Friederich, H. C., Eich, W., & Treede, R. D. (2011). Quantitative sensory testing profiles in chronic back pain are distinct from those in fibromyalgia. Clinical Journal of Pain, 27(8), 682–690. B€ orsbo, B., Gerdle, B., & Peolsson, M. (2010). Impact of the interaction between self-efficacy, symptoms and catastrophising on disability, quality of life and health in with chronic pain patients. Disability and Rehabilitation, 32, 1387–1396. Burckhardt, C. S., Clark, S. R., & Bennett, R. M. (1991). The fibromyalgia impact Questionnaire: Development and validation. Journal of Rheumatology, 18, 728–733. Esteve, J., Rivera, J., Salvat, I., Gracia, M., & Alegre, C. (2007). Propuesta de una versi on de consenso del Fibromyalgia Impact Questionnaire (FIQ) para la poblaci on espa~ nola. Reumatologıa Clınica, 3, 21–24. Finan, P. H., Zautra, A. J., & Davis, M. C. (2009). Daily affect relations in fibromyalgia patients reveal positive affective disturbance. Psychosomatic Medicine, 71(4), 474–482. Fishbain, D., Cutler, R., Rosomoff, H., & Rosomoff, R. (1997). Chronic pain associated depression: Antecedent or consequence of chronic pain? a review. Clinical Journal of Pain, 13, 116–137. Geisser, M. E., Gracely, R. H., Giesecke, T., Petzke, F. W., Williams, D. A., & Clauw, D. J. (2007). The association between experimental and clinical pain measures among persons with fibromyalgia and chronic fatigue syndrome. European Journal of Pain, 11, 202–207. Glombiewski, J. A., Sawyer, A. T., Gutermann, J., Koenig, K., Rief, W., & Hofmann, S. G. (2010). Psychological trearments for fibromyalgia: A meta-analysis. Pain, 151(2), 280–295. Graven-Nielsen, T., & Arendt-Nielsen, L. (2010). Assessment of mechanisms in localized and widespread musculoskeletal pain. Nature Reviews Rheumatology, 6, 599–606. H€auser, W., Brahler, E., Wolfe, F., & Henningsen, P. (2014). Patient health questionnaire 15 as a generic measure of severity in fibromyalgia syndrome: Surveys with patients of three different settings. Journal of Psychosomatic Research, 76(4), 307–311.
H€auser, W., Thieme, K., & Turk, D. C. (2010). Guidelines on the management of fibromyalgia syndrome: A systematic review. European Journal of Pain, 14, 5–10. Herrero, M. J., Blanch, J., Pei, J. M., De Pablo, J., Pintor, L., & Bulbena, A. (2003). A validation study of the hospital anxiety and depression scale (HADS) in a Spanish population. General Hospital Psychiatry, 25, 277–283. Kamping, S., Bomba, I. C., Kanske, P., Diesch, E., & Flor, H. (2013). Deficient modulation of pain by a positive emotional context in fibromyalgia patients. Pain, 154, 1846–1855. Laursen, B. S., Bajaj, P., Olesen, A. S., Delmar, C., & Arendt-Nielsen, L. (2005). Health related quality of life and quantitative pain measurement in females with chronic nonmalignant pain. European Journal of Pain, 9, 267–275. Lled o, A., Pastor, M. A., Pons, N., L opez-Roig, S., RodrıguezMarın, J., & Bruehl, S. (2010). Control beliefs, coping and emotions: Exploring relationships to explain Fibromyalgia health outcomes. International Journal of Clinical and Health Psychology, 10, 459–476. Luciano, J. V., Barrada, J. R., Aguado, J., Osma, J., & GarciaCampayo, J. (2013). Bifactor analysis and construct validity of the HADS: A cross-sectional and longitudinal study in fibromyalgia patients. Psychological Assessment, 26, 395–406. Markkula, R., Kalso, E., Huunan-Seppala, A., Koskenvuo, M., Koskenvuo, K., Leino-Arjas, P., & Kaprio, J. (2011). The burden of symptoms predicts early retirement: A twin cohort study on fibromyalgia-associated symptoms. European Journal of Pain, 15, 741–747. Martın-Arag on, M., Pastor, M. A., Lled o, A., Terol, M. C., Rodrıguez Marın, J., & L opez Roig, S. (2001). Percepci on de control en el sındrome fibromialgico. Psicothema, 13, 568– 591. Martın-Arag on, M., Pastor, M. A., Rodrıguez-Marın, J., March, M. J., Lled o, A., & L opez-Roig, S. (1999). Percepci on de auto-eficacia en dolor cr onico: Adaptaci on y validaci on de la Chronic Pain Self-Efficacy Scale. Revista de Psicologıa de la Salud, 11, 53–76. Mir o, E., Martınez, M. P., Sanchez, A. I., Prados, G., & Medina, A. (2011). When is pain related to emotional distress and daily functioning in fibromyalgia syndrome? the mediating roles of self-efficacy and sleep quality. British Journal Health Psychology, 16, 799–814. Moioli, B., & Merayo, L. A. (2005). Effects of psychological intervention on pain and emotional state of persons with fibromyalgia. Revista de la Sociedad Espa~ nola del Dolor, 12, 476–484. Park, S. H., & Sonty, N. (2010). Positive affect mediates the relationship between pain-related coping efficacy and interference in social functioning. Journal of Pain, 11, 1267– 1273. Pastor, M. A., Lled o, A., Pons, N., & L opez-Roig, S. (2012). Dolor y fibromialgia. Aportaciones desde la Psicologıa. In C. Pe~ nacoba (Ed.), Fibromialgia y promoci on de la salud. Herramientas de intervenci on psicosocial (pp. 77–122). Madrid: Dykinson.
68
Pe~ nacoba Puente et al.
Price, D. D., Patel, R., Robinson, M. E., & Staud, R. (2008). Characteristics of electronic visual analogue and numerical scales for ratings of experimental pain in healthy subjects and fibromyalgia patients. Pain, 140(1), 158–166. http:// www.sciencedirect.com/science/help/doi.htm. Rehm, S. E., Koroschetz, J., Gockel, U., Brosz, M., Freynhagen, R., T€ olle, T. R., & Baron, R. (2010). A crosssectional survey of 3035 patients with fibromyalgia: Subgroups of patients with typical comorbidities and sensory symptom profiles. Rheumatology, 49(6), 1146–1152. Rivera, J. (2012). La fibromialgia en el sistema sanitario espa~ nol. Generalidades e Impacto en la calidad de vida. In C. Pe~ nacoba (Ed.), Fibromialgia y promoci on de la salud. Herramientas de intervenci on psicosocial (pp. 45–73). Madrid: Dykinson. Sandın, B., Charot, P., Lostao, L., Joiner, T. E., Santed, M. A., & Valiente, R. M. (1999). Escala PANAS de afecto positivo y negativo: Validaci on Factorial y convergencia transcultural. Psicothema, 11, 37–51. Sarzi-Puttini, P., Atzeni, F., Salaffi, F., Cazzola, M., Benucci, M., & Mease, P. J. (2011). Multidisciplinary approach to fibromyalgia: What is the teaching? Best Practice & Research. Clinical Rheumatology, 25, 311–319. Schiaffmo, K. M., & Revenson, T. A. (1992). The role of perceived self-efficacy, perceived control, and causal attributions in adaptation to rheumatoid arthritis: Distinguishing mediator from moderator effects. Personality and Social Psychology Bulletin, 18(6), 709–718. Smith, H. S., Harris, R., & Clauw, D. (2011). Fibromyalgia: An afferent processing disorder leading to a complex pain generalized syndrome. Pain Physician, 14, E217–E245. Sobel, M. E. (1982). Asymptotic intervals for indirect effects in structural equations models. In S. Leinhart (Ed.), Sociological methodology (pp. 290–312). San Francisco: Jossey-Bass. Spaeth, M. (2013). Fibromyalgia syndrome review. Journal of Musculoskeletal Pain, 21(2), 178–182. Staud, R., Vierck, C. J., Robinson, M. E., & Price, D. D. (2006). Overall fibromyalgia pain is predicted by ratings
of local pain and pain-related negative affect. Possible role of peripheral tissues. Rheumatology, 45, 1409–1415. Vallejo, M. A., Rivera, J., Esteve-Vives, J., & RodrıguezMu~ noz, M. F. (2012). Uso del cuestionario Hospital Anxiety and Depression Scale (HADS) para evaluar la ansiedad y la depresi on en pacientes con fibromialgia. Revista de Psiquiatrıa y Salud Mental, 5, 107–114. Van Liew, C., Brown, K. C., Cronan, T. A., & Bigatti, S. M. (2013). The effects of self-efficacy on depression and pain in fibromyalgia syndrome: Does initial depression matter? Journal of Musculoskeletal Pain, 21(2), 113–125. Vanderweeen, L., Oostendorp, R. B., Vaes, P., & Duquet, W. (1996). Pressure algometry in manual therapy. Manual Therapy, 1, 258–265. Velasco, L., Zautra, A., Pe~ nacoba, C., L opez-L opez, A., & Barjola, P. (2010). Cognitive-affective assets and vulnerabilities: Two factors influencing adaptation to fibromyalgia. Psychology and Health, 25, 197–212. Watson, D., Clark, L. A., & Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: The PANAS scales. Journal of Personality Social Psychology, 54, 1063–1070. Wolfe, F., Clauw, D. J., & Fitzcharles, M. A. (2010). The American College of Rheumatology Preliminary Diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care and Research, 62, 600–610. Wolfe, F., Smythe, H. A., & Yunus, M. B. (1990). The American College of Rheumatology 1990 criteria for classification of fibromyalgia: Report of the multicentre criteria committee. Arthritis Rheumatology, 33, 160–172. Woo, K. Y. (2012). Chronic wound-associated pain, psychological stress, and wound healing. Surgical Technology International, 22, 57–65. Zigmond, A. S., & Snaith, R. P. (1983). The hospital anxiety and depression scale. Acta Psychiatric Scandinavian, 67, 361–370.
