Perceived Injustice Helps Explain the Association Between Chronic Pain Stigma and Movement-Evoked Pain in Adults with Nonspecific Chronic Low Back Pain

Abstract

Objective

For most patients with chronic low back pain (cLBP), the cause is “nonspecific,” meaning there is no clear association between pain and identifiable pathology of the spine or associated tissues. Laypersons and providers alike are less inclined to help, feel less sympathy, dislike patients more, suspect deception, and attribute lower pain severity to patients whose pain does not have an objective basis in tissue pathology. Because of these stigmatizing responses from others, patients with cLBP may feel that their pain is particularly unjust and unfair. These pain-related injustice perceptions may subsequently contribute to greater cLBP severity. The purpose of this study was to examine whether perceived injustice helps explain the relationship between chronic pain stigma and movement-evoked pain severity among individuals with cLBP.

Methods

Participants included 105 patients with cLBP who completed questionnaires assessing chronic pain stigma and pain-related injustice perception, as well as a short physical performance battery for the assessment of movement-evoked pain and physical function.

Results

Findings revealed that perceived injustice significantly mediated the association between chronic pain stigma and cLBP severity (indirect effect = 6.64, 95% confidence interval [CI] = 2.041 to 14.913) and physical function (indirect effect = −0.401, 95% CI = −1.029 to −0.052). Greater chronic pain stigma was associated with greater perceived injustice (P = 0.001), which in turn was associated with greater movement-evoked pain severity (P = 0.003).

Conclusions

These results suggest that perceived injustice may be a means through which chronic pain stigma impacts nonspecific cLBP severity and physical function.

Introduction

Chronic low back pain (cLBP) is among the most prevalent painful conditions in the United States and worldwide [1]. Although some patients with cLBP have clear pathoanatomic causes of their pain, for most others there is no clear association between pain and identifiable pathology of the spine or associated tissues [2]. This medically unexplained pain is often termed “nonspecific” and happens to be the most common form of cLBP [3]. The problem for those with nonspecific cLBP is that observers tend to react with uncertainty and confusion to patients whose pain is not clearly medically understood. As a result, patients with nonspecific cLBP are prone to the stigmatizing reactions of others. Stigma refers to the disapproval/discrediting of, or discrimination against, a person who is deemed to possess undesirable characteritics that deviate from social norms [4]. Chronic pain stigma may manifest because nonspecific chronic pain deviates from the commonly held belief that pain is the direct result of an identifiable injury or pathology [5]. Chronic pain stigma can have negative consequences for those who have been stigmatized [6]. For example, laypersons and health care providers alike are less inclined to help, feel less sympathy, dislike patients more, suspect deception, and attribute lower pain severity to patients whose pain does not have an objective basis in tissue pathology [7–10]. From the patient’s perspective, qualitative evidence indicates that these individuals often feel invalidated by significant others, friends, and family because of their pain [11, 12]. Some patients report believing that practitioners think their pain is exaggerated or imagined [13]. They feel devalued, blamed, and even report being dismissed by health care providers [14–16]. Stigmatization perpetrated by others can become internalized if patients with cLBP begin to endorse negative feelings and beliefs about their cLBP and apply them to the self. For example, people with chronic pain report feeling inferior to others who do not have chronic pain [17]. Experiences of chronic pain stigma have recently been found to be associated with greater pain catastrophizing, as well as depressive symptom severity and poorer physical functioning [17].

Because of these stigmatizing responses from others, patients with cLBP may feel that their pain is being devalued and discredited, especially when the pain is medically unexplained (i.e., nonspecific). Accordingly, stigmatization due to cLBP may be be perceived as an injustice by those patients who encounter the stigma [6, 18]. Perceived (pain-related) injustice is a risk factor for poor cLBP outcomes [18, 19]. Perceived injustice is conceptualized as a set of cognitive appraisals reflecting the severity and irreparability of pain-related loss, externalized blame, and unfairness [20]. Perceived injustice is positively associated with greater pain severity, disability, and depression across a number of chronic pain conditions [21–23]. Despite both chronic pain stigma and perceived injustice being associated with a range of negative pain outcomes, the pathways that link both constructs to cLBP remain unclear. If patients who experience chronic pain stigma do indeed perceive the stigmatization to be unfair, it may be that perceived injustice could help explain the association between chronic pain stigma and cLBP.

This study sought to examine the associations among chronic pain stigma, perceived injustice, and movement-evoked pain in adults with nonspecific cLBP. Physical activity is often the primary driver of pain symptoms (i.e., movement-evoked pain) in musculoskeletal pain conditions such as cLBP [24]. Therefore, we chose to focus on movement-evoked pain severity in this study rather than a validated pain questionnaire in order to maximize the ecological validity of our results. We tested the following primary hypotheses: 1) chronic pain stigma is significantly and positively associated with perceived injustice and movement-evoked pain; 2) perceived injustice is significantly and positively associated with movement-evoked pain; and 3) perceived injustice mediates the association between chronic pain stigma and movement-evoked pain. Figure 1 illustrates the putative conceptual model representing hypothesis 3. Although not the primary focus, we also tested the hypothesis that perceived injustice mediates the association between chronic pain stigma and physical function.

Figure 1.

Mediation model representing the indirect association of chronic pain stigma with movement-evoked pain through perceived injustice.

Methods

Study Overview

This study is part of a larger ongoing investigation examining ethnic/racial differences in cLBP severity and disability (Examining Racial And SocioEconomic Disparties in cLBP [ERASED]). The ERASED cLBP study incorporates a socioeconomic framework from which to consider differences in cLBP outcomes between black and white adults, as well as the biopsychosocial variables that predict these differences. The participants described in the current analysis were recruited between November 2017 and August 2019 and have not previously been included in any published literature. Findings from the present study were presented in poster format at the 2019 Annual Scientific Meeting of the American Pain Society [25]. The measures and procedures described below are limited to those involved in the current study. A flow diagram depicting matriculation through the study is presented in Figure 2. Individuals with cLBP who were interested in being part of this study were assessed for eligibility during an initial telephone screening with a subsequent review of electronic medical records. Eligible participants completed two separate laboratory-based study sessions. During the first study session, they provided sociodemographic information and completed measures of chronic pain stigma and depressive symptoms. Participants then returned for their second study session one week later and completed measures of perceived injustice as well as movement-evoked pain and physical function. Movement-evoked pain and physical function were assessed by having participants complete a standardized short physical performance battery [26]. Study procedures were consistent with the research standards for cLBP proposed by the Research Task Force of the National Institutes of Health Pain Consortium [27]. All procedures were reviewed and approved by the Institutional Review Board at the University of Alabama at Birmingham and carried out in accordance with guidelines for the ethical conduct of research.

Figure 2.

Flow diagram depicting matriculation through the study. CES-D = Center for Epidemiologic Studies–Depression scale; IEQ = Injustice Experiences Questionnaire; ISCP = Internalized Stigma of Chronic Pain Scale.

Participants

Participants were recruited via flyers posted at the Pain Treatment Clinic within the UAB Department of Anesthesiology and the surrounding community. Participants were included in this study if they were active patients at the UAB Pain Treatment Clinic and reported cLBP that had persisted for at least three consecutive months and was present on at least half the days in the past six months [28]. Furthermore, participants were only included if they denied any type of surgery on the low back or significant trauma/accident within the past year. Low back pain had to be the primary pain complaint reported for all participants with cLBP. To examine the full range of cLBP severity, there was no minimum threshold of self-reported pain intensity for inclusion in this study. All participants had to be between the ages of 18 and 85 years; able to read, write, and understand English; and self-identify as non-Hispanic black/African American or non-Hispanic white/Caucasian. In this study, 105 participants with nonspecific cLBP were included. Informed consent for study participation was obtained from each participant before initiating study procedures.

Initial Screening and Review of Medical Records

All participants completed initial screening via telephone to determine eligibility for study inclusion. A brief health history was obtained, followed by review of medical records to confirm cLBP diagnosis and corroborate self-reported brief health history. Medical records were also reviewed to document any other comorbid diagnoses and analgesic medication use. Participants were excluded from participation for the following reasons: 1) cLBP attributable to specific factors such as ankylosing spondylitis, infection, malignancy, compression fracture or other trauma; 2) presence of systemic rheumatic conditions (e.g., rheumatoid arthritis, systemic lupus erythematosus, fibromyalgia); 3) evidence of uncontrolled hypertension (i.e., SBP/DBP >150/95) or cardiovascular or peripheral arterial disease; 4) poorly controlled diabetes (HbA1c >7%); 5) neurological disease (e.g., Parkinson’s, multiple sclerosis, epilepsy); 6) serious psychiatric disorder requiring hospitalization within the past 12 months; and 7) pregnancy.

Laboratory-Based Study Sessions

During the first study session, participants provided sociodemographic information including age, gender, ethnicity/race, annual household income, educational attainment, and occupational status. They also provided information regarding the current use of prescribed and over-the-counter analgesic medications including opioids, as well as whether they were receiving social security disability benefits. Participants then completed measures assessing self-reported chronic pain stigma and depressive symptoms. One week after the first study session, participants returned to the laboratory and completed a second study session that included additional measures of perceived injustice, movement-evoked pain, and physical function.

Given that participants were primarily recruited from a pain treatment clinic, many were actively prescribed daily analgesic medications including opioids. Participants using daily opioids were not excluded, as this could have undermined the generalizability of study results. Furthermore, they were not asked to withhold opioid pain medications on the days of study participation. This is because temporary withdrawal from these medications could have affected pain perception. Rather, all medications currently prescribed for pain (e.g., opioids, nonsteroidal anti-inflammatory drugs, muscle relaxers, etc.) were recorded and controlled in statistical analyses as needed.

Measures

Chronic Pain–Related Stigma

Participants self-reported their perceptions of chronic pain–related stigma using the Internalized Stigma of Chronic Pain (ISCP) scale [17]. This measure includes 21 items that assess five subscale domains pertaining to enacted and internalized chronic pain stigma: alienation, stereotype endorsement, discrimination experience, social withdrawal, and stigma resistance (reverse-coded before inclusion in the total score). Previous work has indicated that the stereotype endorsement subscale is not sufficiently reliable and does not fit well with the other subscales [17]. Accordingly, it is recommended that it be omitted and that the chronic pain stigma total score only be comprised of the four remaining subscales. Items are measured on a four-point Likert-type scale (1 = strongly disagree to 4 = strongly agree), and the internalized chronic pain stigma total score is calculated by taking the average of the following four subscale domains: alienation, discrimination experience, social withdrawal, stigma resistance (range = 1–4). Higher scores represent greater experiences of chronic pain stigma. The ISCP scale used in this study had acceptable internal consistency (Cronbach’s α = 0.724).

Depression

Depressive symptoms were assessed using the Center for Epidemiological Studies–Depression scale (CES-D) [29]. This 20-item measure assesses the frequency of experiencing depressive symptoms over the past week (0 = never or rarely to 3 = most of the time/all the time). Symptoms of depression measured by the CES-D include negative mood, guilt/worthlessness, helplessness/hopelessness, psychomotor retardation, loss of appetite, and sleep disturbance. This measure has been shown to be reliable and valid in general populations, including when used in chronic pain populations. Responses are summed (range = 0–60), with higher scores indicating greater severity of depression. The CES-D in this study demonstrated excellent internal consistency (Cronbach’s α = 0.919).

Perceived Injustice

The Injustice Experience Questionnaire (IEQ) was used to assess perception of pain-related injustice in this sample of people with cLBP [19]. Participants rated the frequency with which they experienced each of 12 thoughts/feelings when reflecting on their chronic pain condition. Items are rated on a scale of 0 = never to 4 = all the time. IEQ items broadly reflect the associated factors of “severity/irreparability of loss” and “blame/unfairness.” Representative severity/irreparability items include “Most people don’t understand how severe my condition is” and “My life will never be the same.” Blame/unfairness items include “I am suffering because of someone else’s negligence” and “It all seems so unfair.” Responses are summed (0–48), with higher scores reflective of greater perceived injustice. The IEQ has demonstrated strong psychometric properties among individuals with persistent musculoskeletal pain [19, 30]. In this study, the IEQ demonstrated excellent internal consistency (Cronbach’s α = 0.950).

Movement-Evoked Pain and Physical Function

The Short Physical Performance Battery (SPPB) assesses lower extremity function with balance, chair, and walking tests [26]. Specifically, participants were asked to 1) stand with their feet together in the side-by-side, semitandem, and tandem positions for up to 10 seconds each; 2) rise from a seated position in a chair and return to a seated position five times; and 3) walk a four-meter course twice. If the participant did not feel it was safe to perform the activity, they received a score reflecting nonparticipation. For each category, based on their performance, they received a score of 0–4 (total score 0–12). A lower score indicates worse function and greater likelihood of disability. Participants also used a 0–100 (0 = no pain, 100 = the most intense pain imaginable) numeric rating scale to indicate the intensity of any movement-evoked pain in the low back experienced during completion of the balance, chair, and walking tests. The SPPB has been standardized and previously used in populations with cLBP as a measure of lower extremity function [31, 32].

Data Analysis

All data were analyzed using SPSS, version 24 (IBM, Chicago, IL, USA). All participants provided complete demographic data (e.g., sex, age, and ethnicity/race); however, a small portion of missing data existed for self-report questionnaires (<5% for any one questionnaire). Data were deemed to be missing at random, and therefore a simple data imputation method was completed using the macro for Hot Deck imputation. This data imputation method is well validated and accepted in the statistical community [33, 34] and resulted in complete study data for each of the 105 participants. Pearson’s correlations were used to evaluate the associations among continuously measured variables, whereas t tests were used to examine group differences.

To test our primary hypothesis, the PROCESS macro created and described by Hayes [35] for obtaining a bootstrapped 95% confidence interval with 5,000 resamples was utilized to test whether pain-related injustice perception significantly mediated the association between chronic pain stigma and chronic low back pain severity. Bootstrapping is a nonparametric resampling procedure that has been shown to be a viable alternative to normal-theory tests of the intervening mediator between the independent and dependent variables [36]. The 95% confidence interval was incorporated to help minimize the potential of Type I error related to the test of the indirect effect. The bootstrapping technique indicates whether the total effect (path c) of chronic pain stigma on cLBP severity is comprised of a significant mediated effect (a × b). Path a denotes the effect of chronic pain stigma on perceived injustice, whereas path b is the effect of perceived injustice on movement-evoked pain. Study variables that emerged as significantly associated with perceived injustice and/or cLBP severity were included in the mediation model as statistical covariates.

Results

Participant Characteristics

Overall participant characteristics and descriptive information for this sample with cLBP are displayed in Table 1. The mean age of this study’s sample (SD) was 45.8 (13.9) years, with a range of 18–82 years. The study sample consisted of more women (59%) than men (41%), and participants’ sex was coded as 1 = men and 2 = women. The ethnic/racial composition of the study’s sample was 54.3% non-Hispanic black and 45.7% non-Hispanic white. Ethnicity/race was coded as 1 = non-Hispanic black and 2 = non-Hispanic white. The greatest proportion of the sample (39%) reported an annual household income between $0 and $24,999, whereas the vast majority of the sample reported attaining a high school diploma/GED or greater education. The majority of participants reported their occupational status as employed, either full- or part-time (57.2%), followed by unemployed (17.1%), receiving disability benefits (17.1%), and retired (9.6%). Approximately 70% of participants reported current active use of either a prescribed or over-the-counter analgesic medication for cLBP. Analgesic use was coded as 1 = not currently using and 2 = currently using. Of the 70% who reported current use of analgesic medication, the most commonly used class of medication was nonsteroidal anti-inflammatory drugs (51.4%), followed by opioids (25.7%), acetaminophen (10.8%), polypharmacy (9.4%), and muscle relaxants (2.7%). The mean level of movement-evoked pain in response to completion of the SPPB (SD) was 25.9 (29.7) for balance, 35.6 (31.8) for transition from seated in a chair to standing, and 21.7 (28.2) for walking, with a range of 0 to 100 for all three tests. The mean level of physical functioning on the SPPB was ∼9.6 (1.9), with a range of 5 to 12.

Table 1.

Participant characteristics and descriptive data (N = 105)

Variables	No. (%)	Mean (SD)	Range
Age, y		45.79 (13.90)	18–82
Sex
Men	43 (41.0)
Women	62 (59.0)
Ethnicity/race
Non-Hispanic white	48 (45.7)
Non-Hispanic black	57 (54.3)
Annual household income
$0–$24,999	41 (39.0)
$25,000–$49,999	22 (21.0)
$50,000–$74,999	18 (17.1)
$75,000–$99,999	10 (9.6)
$100,000–above	14 (13.3)
Educational attainment
<High school	7 (6.7)
High school diploma/GED	22 (21.0)
Partial college/vocational degree	31 (29.5)
College degree	26 (24.8)
Graduate/professional degree	19 (18.1)
Occupational status
Employed (full/part-time)	60 (57.2)
Unemployed	18(17.1)
Retired	9 (8.6)
Disability benefits	18 (17.1)
Analgesic use
Yes	73 (69.5)
No	32 (30.5)
CES-D		17.88 (11.55)	0–47
ISCP		1.79 (0.51)	1–3
IEQ		17.95 (13.38)	0–44
SPPB–Pain		27.37 (27.41)	0–100
SPPB–Physical Function		9.46 (1.85)	5–12

CES-D = Center for Epidemiologic Studies–Depression Scale; ISCP = Internalized Stigma of Chronic Pain Scale; IEQ = Injustice Experiences Questionnaire; SPPB = Short Physical Performance Battery.

Correlations

The intraclass correlation coefficient for the different movement-evoked pains measured in response to the balance, chair, and walking tests was 0.86. Given this excellent measurement reliability, the repeated movement-evoked pain measurements were averaged together to create a single variable representing movement-evoked pain. Zero-order correlations are presented in Table 2. Greater chronic pain stigma was significantly correlated with greater movement-evoked pain (r = 0.413, P < 0.001), poorer physical function (r = −0.385, P < 0.001), and greater perceived injustice (r = 0.641, P < 0.001), as well as greater depressive symptoms (r = 0.525, P < 0.001). Greater perceived injustice was significantly correlated with greater movement-evoked pain (r = 0.496, P < 0.001) and poorer physical function (r = −0.422, P < 0.001).

Table 2.

Pearson’s correlations

Variable	1	2	3	4	5	6
Age	___
2. Income	−0.089	___
3. CES-D	−0.183	−0.354**	___
4. ISCP	0.199*	−0.473**	0.525**	___
5. IEQ	0.199*	−0.465**	0.505**	0.641**	___
6. SPPB–Pain	0.089	−0.417**	0.206*	0.413**	0.496**	___
7. SPPB–Physical Function	−0.261**	0.272**	−0.120	−0.385**	−0.422**	−0.444**

CES-D = Center for Epidemiologic Studies–Depression scale; IEQ = Injustice Experiences Questionnaire; ISCP = Internalized Stigma of Chronic Pain scale; SPPB = Short Physical Performance Battery.

^* P < 0.05; **P < 0.01.

Selection of Statistical Covariates

Greater movement-evoked pain was significantly correlated with lower annual household income (r = −0.417, P < 0.001) and greater depressive symptoms (r = 0.206, P = 0.035), whereas poorer physical function was significantly correlated with older age (r = −0.261, P = 0.007) and lower annual household income (r = 0.272, P = 0.005). Non-Hispanic black participants with cLBP had significantly greater movement-evoked pain (t = 2.87, P = 0.005) and poorer physical function (t = 2.28, P = 0.025) compared with their non-Hispanic white counterparts. Men with cLBP reported significantly greater chronic pain stigma (t = 2.79, P = 0.006), perceived injustice (t = 2.78, P = 0.005), and movement-evoked pain (t = 2.69, P = 0.009) compared with women with cLBP. Lastly, participants with cLBP who reported actively using analgesic medications for their pain reported significantly greater depressive symptoms (t = 2.08, P = 0.041), greater chronic pain stigma (t = 2.31, P = 0.023), and greater perceived injustice (t = 3.11, P = 0.002) compared with those not actively using analgesic medications. Age, sex, ethnicity/race, annual household income, analgesic use, and depressive symptoms were subsequently included as statistical covariates in the mediation analyses examining the associations among chronic pain stigma, perceived injustice, movement-evoked pain, and physical function.

Mediation

The overall mediation model adjusted for covariates shown in Figure 3 accounted for a significant 36% of the total variance in movement-evoked pain (R² = 0.355, P < 0.001). The mediation effect (path a × b) of chronic pain stigma on movement-evoked pain through perceived injustice had a point estimate of 6.6430 and a 95% confidence interval of 2.0400 to 14.9130. This confidence interval suggests that, even after statistically controlling covariates, the mediated effect represented by a × b is significantly different from zero (i.e., the null effect) at P < 0.05. The directions of paths a (t = 3.41, P = 0.001) and b (t = 3.09, P = 0.003) are consistent with the interpretation that greater chronic pain stigma is associated with greater perceived injustice, which in turn, is associated with greater movement-evoked pain. Thus, perceived injustice was a significant mediator of the association between chronic pain stigma and movement-evoked pain in this sample with cLBP.

Figure 3.

Perceived injustice significantly mediates the association between chronic pain stigma and movement-evoked pain.

Given the temporal aspect of this study (i.e., two study sessions separated by seven days), it is unlikely that movement-evoked pain and perceived injustice, which were measured during the second study session, could have affected chronic pain stigma, which was measured one week prior during the first study session. Indeed, results of an additional mediation model that included movement-evoked pain as the independent variable, perceived injustice as the mediator, and chronic pain stigma as the dependent variable revealed nonsignificant mediation (point estimate of 0.0015 and 95% confidence interval = −0.0016 to 0.0047). This lack of significance lends further credence to the validity of our original hypothesis that greater chronic pain stigma is associated with greater perceived injustice, which, in turn, is associated with greater movement-evoked pain.

A final mediation model was analyzed to determine whether perceived injustice mediated the association between chronic pain stigma and physical function. Results revealed a significant mediation effect with a point estimate of −0.4019 and a 95% confidence interval of −1.0292 to −0.0524. The directions of paths a (t = 3.4097, P = 0.001) and b (t = −2.6280, P = 0.011) are consistent with the interpretation that greater chronic pain stigma is associated with greater perceived injustice, which, in turn, is associated with poorer physical function.

Discussion

The purpose of this study was to investigate the relationships among chronic pain stigma, perceived injustice, and movement-evoked pain in a sample of adults with nonspecific cLBP. Consistent with our hypotheses and previous research [6, 17], greater chronic pain stigma was significantly correlated with greater perceived injustice and movement-evoked pain. Greater perceived injustice was also significantly correlated with greater movement-evoked pain. Notably, perceived injustice significantly mediated the relationships between chronic pain stigma and both movement-evoked pain and physical function outcomes.

A growing number of studies have demonstrated that individuals with medically unexplained pain are vulnerable to stigmatizing reactions from others. In particular, De Ruddere and Craig posit that pain in the absence of observable tissue damage deviates from the widely accepted biomedical model of pain, which presumes that only physiological processes contribute to the pain experience [5]. Consequently, friends, family members, and health care providers may react in stigmatizing ways by discrediting the individual’s pain and socially excluding such individuals [37]. The experience of chronic pain stigma, and the accompanying invalidation and social rejection, may subsequently exacerbate the experience of chronic pain for these stigmatized individuals [38]. The biopsychosocial model of pain provides a framework for understanding how social factors such as stigma affect the brain and biology, which may lead to worse chronic pain outcomes [39]. For example, previous evidence suggests an overlap in the neural systems underlying the distress that arises from social rejection and the pain of a physically noxious stimulus [40]. It appears that social rejection activates pain-related neural regions, thereby sensitizing people for the experience of pain [41, 42]. Furthermore, De Ruddere and Craig suggest that individuals who experience chronic pain stigma are at increased risk of negative psychological outcomes [5]. It may be that the repeated experience of stigmatizing reactions from others leads to diminished self-esteem and hope, as well as greater pain-related perceptions of injustice, all of which can collectively undermine efforts for successful chronic pain self-management. Additional research is warranted to address these possibilities.

Current results are consistent with prior research demonstrating that perceived injustice is associated with greater pain severity and poorer physical functioning among individuals with chronic musculoskeletal pain [18, 19, 21, 22, 43]. Although research examining the underlying mechanisms of perceived injustice effects on pain and functional limitations is sparse, Scott and colleagues reported that anger helped explain the relationship between perceived injustice and chronic pain [44]. Although not directly addressed in this study, individuals with nonspecific cLBP who experience stigma because of their pain may react with anger toward those who they believe are perpetrating the stigma [14]. As a result, anger expressed toward friends and family members could undermine the quality of social support derived from these sources [45]. Similarly, anger expressed toward health care providers could undermine the therapeutic alliance [46], resulting in suboptimal treatment of cLBP. Whether anger helps explain the effect of perceived injustice on pain outcomes in stigmatized individuals with nonspecific cLBP is a topic that warrants additional research.

The stigmatization of medically unexplained chronic pain conditions like nonspecific cLBP may be exacerbated by demonstrable gender and racial biases in the assessment and treatment of pain [47, 48]. The current study consisted of more women than men and more non-Hispanic black adults with cLBP relative to their non-Hispanic white counterparts. Multiple published studies now highlight the health care inequality faced by both women and black patients [49–52]. For example, in a study of men and women presenting to an emergency department with abdominal pain of unknown origin, women waited significantly longer than men to receive pain medication and were less likely to receive it at all relative to men [53]. Another study found that health care providers were more likely to suggest that women were exaggerating their pain experiences compared with men [54]. Women’s pain was more likely to be attributed to psychosocial causes and to result in a recommendation for psychological treatment, whereas men were more likely to have lab tests ordered and be recommended analgesic medications. Similarly, racial disparities in pain assessment and treatment recommendations are well documented in the United States. Health care providers are more likely to underestimate pain in black patients compared with whites, and this may be attributable to false beliefs about biological differences between blacks and whites (e.g., blacks’ nerve endings are less sensitive than whites’) [47]. As a result, black patients consistently receive less adequate treatment for their pain than white patients do [55]. Taken together, it stands to reason that women and black individuals with nonspecific cLBP may be especially susceptible to stigmatization resulting from the medically unexplained nature of their pain and biases commonly present in health care settings.

Clinical Implications

Our findings have implications for the assessment and treatment of individuals with nonspecific cLBP. In the 2016 President’s Message of the American Academy of Pain Medicine, a patient testimony was included, stating, “Doctors don’t recognize pain they cannot see or diagnose as a specific issue” [56]. There is currently literature attesting to the fact that the vast majority of chronic musculoskeletal pain (including cLBP and knee osteoarthritis) cannot be given a precise pathoanatomical diagnosis [57, 58]. So why does medically unexplained pain continue to be so heavily stigmatized, and what can be done about it? Intervention strategies that address stigma at the interpersonal and intrapersonal levels are described in the literature [59], though evidence supporting these strategies remains lacking [5]. At the interpersonal level, work must be done to increase contemporary knowledge and understanding of chronic pain by providing ample educational opportunities to health care providers and the general public [5]. Treatment and rehabilitation for cLBP have traditionally been guided by an emphasis on structural pathology of the spine and related tissues; however, treatment guided by this paradigm often fails to effectively treat cLBP. It has been suggested that health care providers become more familiar with recent evidence attesting to the importance of neuroplastic changes across the central nervous system, which can promote cLBP even in the absence of identifiable pathology of the spine [60]. Furthermore, health care providers and lay caregivers are prone to experiencing compassion fatigue. Compassion fatigue has been described as the physical and emotional exhaustion that can result from caring for others in pain [61]. Loss of empathy due to compassion fatigue may promote stigmatizing responses toward patients with medically unexplained chronic pain. Fortunately, medical educators have introduced courses and experiences designed to nurture and sustain empathy and compassion [62], which are likely to benefit novice and experienced health care providers.

At the intrapersonal level, interventions that cultivate resilience in the face of stigmatizing reactions from others have been proposed in the literature. Notably, researchers have suggested Acceptance and Commitment Therapy (ACT) and mindfulness-based interventions as potentially effective treatments for individuals impacted by chronic pain stigma and perceptions of injustice [5, 20]. In a recent study by Scott and colleagues, ACT-based treatment was shown to decrease pain-related perceptions of injustice, but ACT did not appreciably decrease stigma as measured by the Stigma Scale for Chronic Illness eight-item version (SSCI-8) [6]. Despite the lack of significant association between ACT and stigma in the study by Scott and colleagues, additional research is needed to either corroborate or refute these findings. It remains theoretically plausible that ACT and mindfulness-based interventions could lessen the impact of stigma and unjust beliefs. These interventions could promote the development of skills to decrease the impact of stigma-related thoughts and feelings, while helping individuals to remain engaged in values-based activities despite stigmatization [63].

Limitations

The current study has several limitations. First, there is currently no accepted gold standard method for measuring chronic pain stigma. Various questionnaires have been used to assess experiences of stigma in individuals with chronic pain, which currently limits the generalizability of results. To illustrate, the recent study by Scott and colleagues utilized the SSCI-8 [6], whereas our study incorporated the ISCP developed by Waugh and colleagues [17]. The SSCI-8 and the ISCP may capture different elements of chronic pain stigma, which limits our ability to compare results with related studies. Second, our study did not directly and specifically capture the sources of chronic pain stigma (e.g., family, friends, health care providers) among individual participants, which may be beneficial to examine in future studies. Third, although this study was designed with a temporal precedence in mind (i.e., ISCP was administered a week before IEQ and movement-evoked pain assessment), we cannot rule out the possibility that the associations among chronic pain stigma, perceived injustice, and pain reports may be bidirectional or co-occurring. That our mediation model was significant when modeled as chronic pain stigma → perceived injustice → movement-evoked pain, but nonsignificant when modeled in reverse, lends credence to our original hypothesis that the experience of chronic pain stigma leads to greater perceptions of pain-related injustice for patients with cLBP and, in turn, greater intensity of movement-evoked pain. Despite these limitations, our findings support growing evidence that highlights the impact of chronic pain stigma and perceived injustice on pain outcomes and related disability. Furthermore, the current findings highlight the importance of addressing how health care providers and laypersons alike interact with individuals with nonspecific cLBP.

Conclusions

In conclusion, this study examined associations among chronic pain stigma, perceived injustice, and movement-evoked cLBP severity as well as physical function. Our findings suggest that pain-related injustice perception may be a cognitive mechanism through which experiences of chronic pain stigma impact cLBP severity and physical function. Our findings reinforce the importance of additional research examining stigma and perceived injustice as targets for psychological intervention, especially among individuals with nonspecific cLBP.

 

Funding sources: Research reported in this publication was supported by the National Institute on Minority Health and Health Disparities of the National Institutes of Health under award number R01MD010441 (BRG). Additional support was also provided by Clinical and Translational Science Award number UL1TR001417, provided to the University of Alabama at Birmingham from the National Institutes of Health Center for Advancing Translational Sciences.

Conflicts of interest: None of the authors have any conflicts of interest to report.