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Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Objective

Fibromyalgia is a disabling, chronic pain condition of unknown etiology. Although many factors have been recognized as important contributors to the pain experiences and functional abilities of fibromyalgia patients, the factors that are most impactful (and therefore represent optimal targets for intervention) are still unclear. The aim of the present study was to examine the pathways among depression, self-efficacy, pain, and physical functioning in a large sample of fibromyalgia patients over a 1-year timeframe.

Methods

Data from 462 participants (441 women) were analyzed using an autoregressive path analytical model with first- and second-order cross-lagged effects.

Results

Self-efficacy was the only significant predictor of depression, physical functioning, and pain intensity ratings across time. Physical functioning at 6 months predicted self-efficacy at 1 year; no other factors related significantly to self-efficacy in the model.

Conclusion

Our model suggests that self-efficacy is a salient factor in fibromyalgia symptomatology. Our findings support designing interventions that use a multimodal approach, with an explicit focus on combining exercise (or other means) to improve physical functioning and psychotherapy (e.g., cognitive–behavioral therapy) with the intention of reprocessing the functional improvements and the implications of these improvements for the patients' ability to manage their fibromyalgia symptoms. By doing so, self-efficacy should be enhanced, and this would produce the greatest and broadest benefits for fibromyalgia patients.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Fibromyalgia syndrome (FMS) is a chronic, painful musculoskeletal disorder of unknown etiology that affects ∼2% of the population in the US (1). FMS is perhaps one of the most difficult conditions to manage for both patients and practitioners because of the uncertainty of the diagnosis and management of the disease. Although many theories have been proposed and have received some level of empirical support (including genetic, neuroendocrine, neurologic, and psychological theories [1–4]), the true etiopathogenesis of FMS remains unknown. Therefore, researchers and clinicians continue to assess the proper means of and targets for effective intervention and treatment.

The American College of Rheumatology (ACR), in its recent provisional diagnostic criteria, has acknowledged the importance of including nonmyalgic factors in the diagnostic criteria for FMS, allowing for a greater variability in the nature of the disease experiences of those for whom the diagnosis of FMS is fitting (5). The inclusion of nonmyalgic factors, and specifically psychological factors, requires that researchers attempt to identify the most important psychological factors in FMS with greater precision (that is, the factors that contribute to the most marked augmentation of the pain experience and therefore represent the most promising targets for intervention).

Although individuals affected by FMS experience numerous and varied complications, pain and poor functioning are chief among them (6, 7). Therefore, pain and poor functioning are the 2 symptoms that researchers and clinicians can agree are important targets for intervention. However, the complex nature of FMS suggests that the pain manifested in FMS cannot and should not be treated like most other forms of pain. For example, centrally acting analgesics, such as opiates, are not effective for treating pain in FMS, although they generally are efficacious frontline treatments for intense pain (8–10).

Psychological factors have been found both to account for variance in pain experienced by people with FMS and to mediate the effectiveness of treatments for FMS (11–13). Therefore, psychological factors have been targeted for intervention in FMS (14, 15). However, the psychological constructs serving as the contributors to pain and its enhancement have not been identified definitively. Thus, a predictive model of the relationships that exist among pain, functioning, and psychological concomitants could provide important information to researchers and health care providers.

Among the psychological factors that have been shown to play an important role in FMS and that are the focus of the present study are self-efficacy and depression. Self-efficacy is the beliefs an individual has about his or her ability to perform a specific task or accomplish a given objective (16). Self-efficacy is an important factor in FMS because FMS is a condition that demands high levels of self-management. Depression is a psychological disorder that occurs with alarming frequency in those with FMS (17, 18) and it has more deleterious implications for this population than for other populations (19–21). Self-efficacy and depression are related to one another and to functioning and pain in many clinical pain populations (22–25); however, the nature of these relationships is not well understood.

The present study examined the longitudinal relationships among self-efficacy, depression, pain, and functioning in a large sample of patients with FMS to construct a better predictive model of how these psychological factors lead to the perpetuation of pain and poor functioning among those with FMS, which in turn will help to identify the most promising targets for intervention.

Significance & Innovations

  • Our study used a large sample of 462 fibromyalgia patients and a longitudinal design (baseline, 6-month, and 1-year time points) to examine the relationships among depression, self-efficacy, pain intensity, and physical functioning.

  • Our study identified self-efficacy as a salient (and the only stable) predictor of depression, pain, and physical functioning across time in fibromyalgia.

  • These findings have important implications for designing interventions to test in randomized clinical trials, suggesting that multimodal approaches should be used with an explicit focus on improving self-efficacy in order to maximize treatment effects across time.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Participants.

Six hundred (574 women) members of a health maintenance organization (HMO) participated in the study. After excluding dropouts and other individuals who had missing assessments, data from 462 participants (441 women) were examined at 3 time points: baseline, 6 months, and 1 year. All participants were required to have a physician's diagnosis of FMS and meet the ACR 1990 criteria for FMS (26). The mean ± SD age of the participants was 54 ± 11.1 years. Most participants (65%) were married, 93% were white, 52% were employed on a full-time or part-time basis, and 83% had completed some level of college education. The participants' median income ranged from $20,000–$40,000.

Measures.

Self-efficacy.

Perceived self-efficacy was measured with the Arthritis Self-Efficacy Scale (ASES) (27), which was modified for FMS patients by changing the term “arthritis” to “fibromyalgia” or “condition,” where necessary. This scale consists of 20 items and measures self-efficacy for pain, daily functioning, and other symptoms. Participants rated their confidence in their abilities to perform certain tasks, such as walk 100 feet on flat ground in 20 seconds. Responses can range from 0 (very uncertain) to 100 (very certain), with higher scores indicating greater self-efficacy. The ASES has been found to have high test–retest (0.71 ≤ r ≤ 0.85) and internal (0.76 ≤ α ≤ 0.89) reliability (27).

Pain.

The present pain intensity index subscale from the McGill Pain Questionnaire (MPQ) (28) was used to assess the current level of pain in participants with FMS. Participants were asked to rate their pain using a 6-point Likert-type scale, where 0 = no pain, 1 = mild, 2 = discomforting, 3 = distracting, 4 = horrible, and 5 = excruciating. Test–retest reliability on the MPQ has been reported at r = 0.70 (28), and construct validity has been previously demonstrated (29).

Depression.

The Center for Epidemiologic Studies Depression Scale (CES-D) (30) is a self-administered measure that assesses depression symptomatology. The CES-D consists of 20 items that are rated on a 4-point Likert-type scale ranging from 0–3, where 0 = rarely or none of the time and 3 = most or all of the time. Scores can range from 0–60, with ≥19 indicating depressed mood for chronic pain populations (31). The CES-D is reliable (0.77 ≤ r ≤ 0.92), is internally consistent (0.80 ≤ α ≤ 0.90), and has moderate test–retest reliability (r = 0.40) and high concurrent and construct validity (30).

Physical functioning.

The Fibromyalgia Impact Questionnaire (FIQ) is a brief 10-item self-administered assessment that measures physical functioning and psychological, social, and global well-being in people with FMS (32). Physical functioning was measured using the first question on the FIQ, which consists of 10 subitems that focus on the ability of a patient to perform large-muscle tasks (e.g., vacuuming a rug). These items are presented in a Likert-type format ranging from 0–3, where 0 = always able to do and 3 = never able to do. The rating scores from the 10 subitems are added together and divided by the number of valid response ratings to obtain a total physical functioning score, with higher scores representing greater impairment in functioning. The FIQ has demonstrated test–retest reliability (0.56 ≤ r ≤ 0.95) and content and construct validity (32).

Procedure.

The patients with FMS were part of a large longitudinal study that measured the effects of social support and education training on health status, health care utilization, and quality of well-being (33). Participants were recruited for the study through newspaper advertisements, mass mailings to HMO members, referrals by physicians, and flyers in physician offices. Participation in the study involved attending 20 two-hour meetings for 1 year and completing a battery of questionnaires at baseline, 3 months, 6 months, 12 months, and 18 months. No monetary compensation was provided to the participants. Because no intervention effects were found in the original study (33), all participants were entered into the analysis. Pairwise t-tests were conducted to examine changes over time for outcome measures. After Bonferroni adjustments (adjusted per comparison, α = 0.004), there was a statistically significant change from baseline to the 6-month assessment for self-efficacy (t[500] = −5.37, P < 0.001) and depression (t[500] = 6.53, P < 0.001). From baseline to 1 year, there was a significant change in scores for depression (t[491] = 10.74, P < 0.001), pain intensity (t[491] = 3.37, P < 0.001), and self-efficacy (t[491] = 8.57, P < 0.001). There was a significant change between the 6-month and 1-year assessments for depression only (t[462] = 3.985, P < 0.001). It appears reasonable to attribute these changes to attention effects that occurred simply as a result of being involved in an intervention study.

Missing data analysis.

Six hundred individuals completed questionnaires upon entry into the study (Time 1), 501 completed assessments at both time 1 (baseline) and time 2 (6 months), and 462 completed measures at time 2 (6 months) and time 3 (1 year). Analyses were conducted to examine the differences between participants who completed the assessments at time 1 and time 3 versus participants who were absent for any assessments. After using a Bonferroni correction (adjusted per comparison, α = 0.012), no significant differences in demographic characteristics or on the variables of interest were found between the 2 groups.

Statistical analysis.

First-order autoregressive path models allow researchers to explore relationships over time, where each time point is linearly predicted by the previous time point. Second-order models consider the relationship between consecutive values, as well as the association between values 2 time periods apart. Second-order autoregressive models are beneficial when values across multiple time points are highly correlated. The addition of cross-lagged effects to an autoregressive model allows researchers to explore reciprocal relationships between variables. The current analysis used an autoregressive path analysis model specifying first- and second-order cross-lagged effect to examine the relationships among pain intensity, physical functioning, depression, and self-efficacy across a 1-year time interval. Cross-lagged effects were estimated to examine reciprocal relationships, because it was hypothesized that the variables would be fairly stable across time.

In the present study, the overall model goodness of fit was assessed using multiple descriptive indices. The fit criteria were the comparative fit index (CFI) (34) and the standardized root mean square of the model residuals (SRMSR). The CFI is scaled from 0.00–1.00 and fit is considered adequate when it is ≥0.90. Additionally, the SRMSR should be ≤0.08 to represent acceptable goodness of fit (35).

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Descriptive analyses and stability coefficients.

Means and SDs for each time point for pain intensity, physical functioning, depression, and self-efficacy are shown in Table 1. Stability and correlation coefficients are shown in Table 2. The stability coefficients for depression, pain intensity, physical functioning, and self-efficacy were all statistically significant and positive across groups.

Table 1. Means and SDs for each time point of the sample
 Mean ± SD
Depression 
 Baseline19.58 ± 11.59
 6 months16.59 ± 10.31
 1 year14.84 ± 9.68
Pain intensity 
 Baseline2.26 ± 0.85
 6 months2.20 ± 0.96
 1 year2.08 ± 0.97
Self-efficacy 
 Baseline56.22 ± 17.88
 6 months60.39 ± 17.66
 1 year62.10 ± 16.48
Physical functioning 
 Baseline1.29 ± 0.69
 6 months1.33 ± 0.71
 1 year1.36 ± 0.71
Table 2. Stability and correlation matrix*
 123456789101112
  • *

    T1 = baseline; T2 = 6 months; T3 = 1 year.

  • Stability coefficient; P < 0.001.

  • P < 0.001.

  • §

    P < 0.01.

1. Functioning T1           
2. Functioning T20.556          
3. Functioning T30.4900.559         
4. Depression T10.4270.3940.343        
5. Depression T20.3470.4290.3000.599       
6. Depression T30.3360.3620.3760.5370.558      
7. Self-efficacy T1−0.491−0.442−0.382−0.482−0.405−0.372     
8. Self-efficacy T2−0.369−0.499−0.401−0.366−0.543−0.3990.598    
9. Self-efficacy T3−0.364−0.495−0.467−0.355−0.451−0.5550.5660.687   
10. Pain T10.2120.287−0.2400.3350.2430.261−0.300−0.237−0.243  
11. Pain T20.132§0.2270.2220.2200.3160.244−0.237−0.324−0.2430.317 
12. Pain T30.2130.2460.3110.2520.2520.329−0.239−0.331−0.3880.3170.329

Autoregressive model results.

An autoregressive path analysis model specifying first- and second-order cross-lagged effect was tested using EQS 6.1 (Multivariate Software). A robust maximum likelihood estimation method was used with the Satorra-Bentler scaled chi-square statistic to adjust for the influence of individual variables that demonstrated kurtosis. All baseline measures were modeled as predictors of physical and psychological outcomes at 6 months, which served as the predictors of the dependent variables at 1 year. The correlations among all predictor variables and dependent variables were also estimated.

The autoregressive model exhibited satisfactory goodness-of-fit statistics (Satorra-Bentler χ2[18] = 135.250, P < 0.001, CFI = 0.937, SRMSR = 0.061). The results for the significant relationships between self-efficacy, physical functioning, depression, and pain are shown in Figure 1. Initial pain intensity ratings, levels of depression, self-efficacy, and physical functioning were significantly correlated with one another at baseline (0.246 ≤ |r| ≤ 0.505) and 1 year (0.127 ≤ |r| ≤ 0.390).

thumbnail image

Figure 1. Autoregressive model of the significant pathways among physical functioning (PHYS FUNC), depression (DEP), self-efficacy (SE), and pain intensity (PAIN) over 1 year in fibromyalgia syndrome. BL = baseline.

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In the model, depression at 6 months was significantly predicted by self-efficacy measured at baseline (β = −0.134), which explained ∼2% of the variance after accounting for the influence of baseline levels of depression (β = 0.519, R2 = 0.384). This relationship was also found for depression at 1 year, with self-efficacy at 6 months significantly explaining ∼1% of the variance in depression (β = −0.085) after accounting for depression levels at 6 months (β = 0.294) and baseline (β = 0.302, R2 = 0.377). Lower levels of depression at 6 months and 1 year were predicted by higher self-efficacy over time. Pain intensity at 6 months and 1 year (β = 0.035 and 0.067, respectively) and physical functioning at 6 months and 1 year (β = 0.067 and 0.061, respectively) did not significantly add to the predictive value of self-efficacy over time.

A similar relationship was found between pain intensity and self-efficacy at 6 months and 1 year. Pain intensity at 6 months was significantly predicted by self-efficacy at baseline (β = −0.126) and pain reported at baseline (β = 0.226), accounting for ∼2% of the explained variance for pain (R2 = 0.099). Self-efficacy measured at 6 months also predicted pain intensity ratings at 1 year (β = −0.198) after accounting for pain ratings at baseline (β = 0.207) and 6 months (β = 0.200, R2 = 0.194). Self-efficacy accounted for ∼4% of the explained variance in pain intensity at 1 year. Participants who had higher levels of self-efficacy reported experiencing less pain over time. Depression at 6 months and 1 year (β = 0.053 and 0.034, respectively) and physical functioning at 6 months and 1 year (β = −0.013 and 0.031, respectively) did not significantly add to the predictive value of self-efficacy over time.

Physical functioning at 6 months was significantly predicted by self-efficacy (β = −0.166), depression (β = 0.113), and pain intensity (β = 0.100) ratings assessed at baseline after accounting for physical functioning at baseline (β = 0.396), with each accounting for 1–2% of the variance in functioning. The participants who reported having better physical functioning at 6 months also reported having better initial physical functioning, lower levels of depression, lower initial pain intensity, and more self-efficacy for their illness at baseline (R2 = 0.370). However, physical functioning at 1 year was significantly predicted by self-efficacy at 6 months (β = −0.124) after accounting for physical functioning at 6 months (β = 0.359) and baseline (β = 0.247, R2 = 0.365). Depression (β = −0.028) and pain intensity (β = 0.084) did not significantly add to the predictive value of self-efficacy at 1 year.

In summary, self-efficacy was the only significant predictor of depression, physical functioning, and pain intensity ratings across time after controlling for the influence of past ratings of psychological and physical functioning. However, self-efficacy at 6 months was predicted by a previous rating of self-efficacy only (β = 0.529), which accounted for ∼28% of the variance in self-efficacy (R2 = 0.370). Depression (β = −0.066), physical functioning (β = −0.071), and pain intensity (β = 0.009) assessed at baseline did not significantly add to the predictive value of self-efficacy. Self-efficacy at 1 year was predicted by physical functioning at 6 months (β = −0.149), as well as self-efficacy at baseline (β = 0.215) and 6 months (β = 0.466, R2 = 0.512), suggesting a complementary relationship between physical functioning and self-efficacy during this time period. Physical functioning explained 2% of the variance in self-efficacy. Depression (β = −0.052) and pain intensity (β = −0.016) assessed at baseline were not significant predictors.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

For the present study, an autoregressive, cross-lagged path analytical model examining longitudinal (baseline, 6 months, and 1 year) data from 462 fibromyalgia patients (441 women) was evaluated. As a whole, the analysis showed that self-efficacy, pain, depression, and functioning in FMS were significantly interrelated. Although the interrelationships in general were not particularly surprising (12), the specific pathways that were identified by the autoregressive analysis provide important new information for researchers in the field of FMS.

Self-efficacy was the only significant predictor of depression, pain, and physical functioning across time, with lower levels of depression, lower levels of pain, and higher levels of physical functioning predicted by higher self-efficacy. The model suggested that individuals who believed they were less able to manage their FMS symptoms were more likely to become depressed. This finding is consistent with the results from a previous study (36) suggesting that self-efficacy is an essential component to consider for understanding depression in FMS. The model also indicated that those who believed they were less able to manage their FMS symptoms were more likely to report experiencing greater pain intensity and functional impairment. Although these findings are not surprising and are supported by a previous study (37), the present study shows that this pattern is consistent across time and highlights the salience of self-efficacy as an explanatory factor for both the physical and psychological symptoms of FMS.

The relationship between self-efficacy and physical functioning was more complex. Physical functioning was the only predictor of subsequent self-efficacy; specifically, physical functioning at 6 months predicted self-efficacy at 1 year. This suggests that a reciprocally influential relationship may exist between self-efficacy and physical functioning. It is easy to imagine how the difficulty patients with low self-efficacy have in managing their FMS symptoms, which in turn results in lower functioning, can lead to further decreases in self-efficacy. Viewed differently, this reciprocal relationship predicts that improving self-efficacy and functioning should generate a salubrious cycle of improvement, not only within these constructs, but also in depression and pain. These findings have important implications for interventions.

At present, many interventions are multimodal and target improvements in fibromyalgia symptoms through self-management, cognitive–behavioral therapy (CBT), or exercise (10). However, the effectiveness of these approaches is limited and short lived, and many researchers have cited large individual variations in treatment response (38–40). Our findings suggest that there is a different approach from those previously put forward. We believe that an effective intervention to reduce depression and pain and to increase physical functioning in FMS may include self-efficacy as the primary target with respect to salience, but with physical functioning as the temporally initial target.

One limitation of the present study is that all of the participants were part of a large HMO in southern California, and this may limit generalizability. However, the characteristics of the sample largely reflect the population affected by FMS. In addition, although the model may seem simplistic, other potential variables of interest were examined, but they did not account for additional variance. Additional research is needed to determine whether variables that were not tested can better explain the changes in pain and physical functioning over time.

Based on these preliminary findings, multimodal interventions that combine psychotherapy (e.g., CBT) and physical exercise (40, 41) and that focus on improving self-efficacy in order to lead to better outcomes in FMS seem most promising. Based upon our model, merely including exercise (or other means) to improve functioning and psychotherapy to manage symptoms is not sufficient to achieve a maximum treatment effect. Rather, our analysis suggests a synergistic approach, specifically, using exercise and therapy combined for patients to experience improvements in functioning, while simultaneously reprocessing these improvements and their implications for one's ability to manage their symptoms. This should enhance feelings of self-efficacy, which should have the greatest, most extensive, and longest-lasting benefits for those with FMS.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Cronan had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Van Liew, Brown, Cronan, Bigatti, Kothari.

Acquisition of data. Cronan, Bigatti.

Analysis and interpretation of data. Van Liew, Brown, Cronan, Bigatti.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES