Modified Perception of Pain in Ethnic Minorities
The Effect of Expectations and Social Exclusion
By: Christopher R Dunne
The perception and response to pain is an essential component of maintaining a person’s wellbeing. Interestingly however, despite the importance of avoiding and reacting to pain, its perception varies widely, and the same stimulus can elicit dramatically different responses among a population. For instance, one stimulus can be below the threshold of pain in one individual while simultaneously being deemed unbearable to another (Nielsen et al., 2005). Clearly, there must be key differences between individuals that impact pain tolerance, threshold, and response. Although there are many known mediators of these differences, (i.e. genetics, current environment, and previous experience) culture is one known mediator that has not been studied to the fullest extent. One reason for this is that culture is extremely broad and encompasses a wide range of factors, and is consequently difficult to quantify. To overcome this obstacle, this paper will examine a subset of culture that can be easily categorized, namely ethnicity, and determine its effect on pain perception in the United States.
Distinctions between ethnic groups are not always sharp and easily defined, and research could examine a large set of potential ethnic groupings. However, due to the complexity of the subject and a dearth of available research, this paper will make a general examination investigating the perception of pain among ethnic minorities (non-Caucasian individuals) versus those of the majority population in the United States (Caucasian individuals). More specifically, this paper aims to examine the perceptual effect caused by the existence of distinct expectations and increased social isolation among ethnic minorities compared to Caucasian individuals. Distinct expectations and increased social isolation are theorized to exist due to the fact that ethnic minorities in the United States receive inferior healthcare and face communication challenges with caregivers. To support this claim, this review elucidates how a history of poor care experienced by minorities leads to low expectations about the success of pain-management treatment, and then links these expectations to enhanced pain. Next, social exclusion of minorities is demonstrated and also linked to enhanced pain. Taken together, these observations support a hypothesis that in general, ethnic minorities perceive more pain than Caucasians when exposed to the same injury.
As an essential component of this paper’s hypothesis, the existence of differing expectations about healthcare outcomes among minorities must be clearly demonstrated. A strong case for this can be built when considering that minorities in the United States consistently receive inadequate medication for injuries, (Cleeland et al., 1994; Cleeland et al., 1997) and are therefore likely to expect similar treatment in the future. Additionally, language difficulties create miscommunication and a lack of understanding that can lead to improper diagnosis and poor pain treatment (Anderson et al., 2003, Teske et al., 1983). Lack of clear communication can also cause minorities to be uncertain about instructions from doctors. Importantly, this communication barrier is widespread among minorities. For example, even among native English speakers, minority groups such as African Americans, Asian Americans, and Latinos report significantly more communication issues with their doctors than Caucasians do (Collins et al., 2002). Following this logic, it can be surmised that many minorities expect less successful healthcare results when they are dealing with doctors with whom they struggle to communicate. Although this expectation is certainly not ubiquitous, its presence is exemplified by the fact that minorities generally express a higher degree of mistrust towards doctors and lack confidence in their knowledge and effort (Lillie-Blanton et al., 2000; La Veist et al., 2000). Taken together, this evidence suggests that pervasive communication challenges and a history of receiving inferior healthcare lead to the expectation among many minorities that visits to their healthcare practitioner will not be successful in eliminating pain and other ailments.
To determine how expectancy impacts pain-perception, one can examine the widespread literature on the topic. Interestingly, this research is conflicting; however, both suggested models can be shown to predict an increase in pain perception by minorities. One competing hypothesis suggests that expecting more pain leads to a direct increase in perceived pain. Evidence for this expectancy driven hypersensitive pain response is consistent with three recent fMRI studies (Fairhurst et al., 2007; Koyama et al., 2005; Ziv et al., 2010) in which participants had their brain activity measured while receiving thermal input ranging from barely perceivable to painful. In some trials, the subjects were visually cued about the advent of a painful stimulus, and on some trials, they were not. The results of these studies showed that cuing painful stimuli resulted in both an increased report of pain and an increased activation of the amygdala and hippocampus (brain areas associated with pain). These results are consistent with a model in which minorities would experience more pain due to their expectancy of inefficient and low quality care. Additionally, a hypersensitive pain response could have an evolutionary advantage, as increased pain cued by expectancy would allow humans to react more quickly and pointedly to an imminent bodily danger.
However, trouble with the hypersensitive hypothesis occurred when Ziv and colleagues (2010) noticed that the perceptual effect in their study was driven by only half of the participants, while the other half of the participants displayed no altered perception following cued pain. The researchers hypothesized that this might be due to different personality types, and that those individuals who are generally less anxious will not report increased pain following a cue. Even if this is true though, it could be argued that most minorities would still fall into the enhanced pain group, as previous experience of poor care would likely make them anxious about future care.
The pathway between expectancy and perceived pain becomes more complicated when considering research that has suggested that expectancy of high pain actually lowers perceived pain (Carlsson et al., 2006). This second model also could make evolutionary sense, as it could be advantageous to temporarily ignore a painful stimulus in order to attend to a pressing issue which may be causing the pain itself. Carlsson et al. (2006) provided support for this hypothesis in a study where they observed the effect of expectancy on pain perception after either cuing a high pain stimulus or presenting it randomly without cues. Their main finding was that when the high pain stimulus was cued, participant showed enhanced activation in their primary and secondary sensory cortex, and when the painful stimulus was not cued, participants showed increased activation in their insula and orbitofrontal cortex. Since the sensory cortex plays a large role in discriminating tactile location while the insula and orbitofrontal cortex are implicated in pain perception, it was hypothesized that when the subjects knew to expect pain, they focused more on determining where the pain was coming from, and less on the actual pain itself. In contrast, when participants did not know when to expect pain, they were anxious about the advent of future pain and therefore very focused on detecting the pain when it did occur.
Despite this apparent incongruity in the literature relating expectancy to pain perception, a closer look at the methods employed in each study suggests a possible way to reconcile the opposing results. Most notably, Carlsson et al. (2006) used shock as the method of induced pain whereas the other studies utilized thermal pain. Given that shock is a more salient stimulus, Carlsson et al. proposed that it is more representative of a major injury, while thermal pain is more representative of a minor injury. Moreover, Carlsson et al. believed that shock would numb pain because it would activate the parasympathetic nervous system and the fight or flight response, while thermal pain would instead heighten senses so that avoidance of a minor injury could be fine-tuned. Therefore, assuming that the pain minorities face does not trigger the fight or flight response, an enhanced perception of pain could still be consistent with the results of Carlsson’s study.
Even if severe injuries do trigger the fight or flight response in minorities though, there is evidence that expectancy could still cause increased pain. This possibility is supported by a hypothesis that was laid out by Ploghaus and colleagues (2001) that states that anxiety determines if an individual undergoes a hypersensitive or numbing response to cued pain. The hypothesis equates high certainty outcomes with low anxiety and low certainty outcomes with high anxiety. From here, it states that if a subject is certain that a cue represents pain, then it will numb pain, but if the subject is not certain that the cue represent pain (and is therefore anxious about the pain), then the cue will result in a hypersensitive pain response. To test this theory, these researchers utilized fMRI in experiments in which given cues were associated with different levels of expectancy towards pain. Specifically, one cue was always followed by a moderate pain stimulus (certain expectancy) while another cue was usually followed by the same moderate pain stimulus but occasionally followed by a high pain stimulus (uncertain expectancy). The researchers found that in the uncertain expectancy condition, the participants showed higher activation of brain areas associated with anxiety. Furthermore, in the uncertain condition the moderate pain stimulus generated a larger pain response than when it was followed by the certainty cue, which was represented by both increased brain activity and self-report. This was hypothesized to occur because in the certain expectancy condition, participants were accepting of the inevitable advent of pain, and therefore focused less on the pain itself. Conversely, in the uncertain expectancy condition, the participants were anxious about the pain, and therefore fully concentrated on it.
Grillion et al. (2008) provided further support for this anxiety hypothesis when they discovered that when an aversive stimulus was unexpected, individuals with panic disorder showed a much higher startle response than controls. This suggested that increased levels of anxiety in those with panic disorder resulted in a lager response to a certain stimulus and supports the fact that anxiety could heighten perception. This ties into perceptual pain among minorities because one would expect that those who have previously received poor care would be more anxious about future care, and therefore be more prone to a larger pain response.
On top of previous experiences creating anxiety which could increase perception of pain, communication challenges could create a situation where minorities would be more anxious and uncertain about what healthcare results to expect. Conceivably, this uncertainty in the level of expected pain could compound the effects of anxiety about perceived pain. In fact, uncertainty was associated with increased pain in a study of Vietnamese and American citizens who fractured their femurs and underwent surgery (in their respective country) to aid in healing (Carragee et al., 1999). Only 4% of the Americans reported that they had a good sense of the pain they would experience after surgery, compared to 76% for Vietnamese patients. Correlated with their uncertainty, the Americans reported a high degree of pain relating to their injury, and half even reported that the pain they experienced must be caused by a complication of some sort. On the other hand, most of the Vietnamese patients reported that their pain was manageable. Further, the Vietnamese patients requested an average of three times less morphine than the Americans did. In summary, the Vietnamese patients had clear initial expectations about their pain and then reported a low degree of pain, while the Americans were unsure about the pain they would face and conversely reported a higher degree of pain. This ties into minority communication challenges because if a person is unable to clearly understand his or her doctor’s explanation of expected pain, that could set the stage for uncertainty and anxiety creating an enhanced perception of pain. This research also suggests that even if high-certainty expectations decrease perceptual pain as Carlsson et al. (2006) suggested, minorities may not see this benefit due to communication challenges with their doctors making their expectancies about future pain ambiguous.
Enhanced pain perception due to altered expectancy and increased anxiety are not the only factors that play into the equation. Rather, increased social isolation among minorities also leads to enhanced pain relative to Caucasians. Although minority groups often have vibrant cultures with strong social support in their homes and neighborhoods, this is not the case in many hospitals and clinics. For starters, the aforementioned language barriers restrict inclusion of minorities in decisions relating to their care, (Ferguson & Candib, 2002) and doctors display less emotion and empathy towards patients who are of different ethnicities than themselves (Hooper et al., 1982; Schouten & Meeuwesen, 2006). One can also imagine that while in a hospital or surgery room, minorities may feel less included by those around them due to differing cultural beliefs. Therefore, it is not hard to accept the existence of social exclusion of minority patients in at least some cases. Subsequently, support for enhanced perceptual pain among minorities will follow if a strong link between social exclusion and pain perception can be built.
Although this link was long suspected, the first neural imaging support for it came in 2003 through an fMRI study by Eisenberger and colleagues. In this study, patients played a virtual ball tossing game (CyberBall) where they believed they were playing with other human individuals in separate fMRI machines; in reality, the other participants were computer programs. At first, the test subjects were included in the ball toss, but after a few throws they were never tossed the ball again. It turned out that the anterior cingulate cortex was more active during exclusion, and this activation correlated positively with reports of distress. This was a breakthrough finding because physical pain also results in increased anterior cingulate cortex activity, and this activity is likewise correlated with increased pain reports (Rainville et al., 1999). With this finding, it becomes apparent that minority patients could have increased pain from injuries compared to white patients, as social exclusion could result in emotional pain that compounds physical pain.
The connection between social exclusion and the perception of pain is not so clean however, as a conflicting study was published in 2006 by DeWall & Baumeister that showed that social exclusion buffered individuals from pain rather than enhanced it. To create the social exclusion or inclusion status, the researchers had participants fill out a personality test and then had a computer seemingly run an analysis that predicted their future. In some cases, the computer predicted that individuals would end up alone and with few friends (social exclusion), and in others it predicted they would end up happily married with numerous friends (social inclusion). The computer also provided actual feedback about the personality test to increase believability in its future life prediction. Intriguingly, and in contrast to previous studies, DeWall & Baumeister found that individuals who were in the social exclusion group had higher pain tolerance and pain thresholds compared to those in the inclusion group.
Although these results seem to conflict with the claim that minorities perceive enhanced pain due to social exclusion, Bernstein and Claypool (2012) recently proposed a hypothesis to reconcile the competing results. Their hypothesis (the severity hypothesis) was parallel to Carlsson’s hypothesis that extreme physical pain results in a buffering effect, while minor physical pain heightened senses. In short, Bernstein and Claypool surmised that extreme social exclusion would lead to a buffering effect while minor social injury would enhance the perception of pain. To set up this experiment, Bernstein and Claypool first ran a pilot study to assess how individuals rated exclusion during the CyberBall game versus exclusion in the future life prediction paradigm. Not surprisingly, subjects reported that the life alone prediction represented a significantly larger social injury than exclusion in the CyberBall game. With this knowledge, the experimenters set up two exclusion versus inclusion groups differing in severity of exclusion. The members of the non-severe group underwent either exclusion or inclusion in the CyberBall game, while the severe group took the personality test and had their futures predicted to be filled with either exclusion or inclusion. In accordance with Bernstein and Claypool’s hypothesis, the subjects who underwent extreme social exclusion (future life alone prediction) experienced a buffering effect to pain, while subjects who underwent minor social exclusion (CyberBall exclusion) experienced an enhancement of pain. Also, the differences were not simply due to an effect of experimentation, as the inclusion groups in each setup had insignificant differences in pain threshold and tolerance before and after the test trials. The researchers then provided further support for their severity hypothesis when they modified the future life paradigm to also include a less severe prediction of future loneliness. Once again, the results showed that the subjects with a less severe exclusion prediction had a heightened pain response while the subjects with a more severe social exclusion prediction showed a buffered pain response.
If one accepts the severity hypothesis, its implications on minorities’ perception of pain can then be assessed. Unfortunately, no research was found which quantified the degree of social exclusion typically faced by minorities in healthcare settings. Nevertheless, it is hypothesized here that aside from extreme cases, the social exclusion faced by minorities would not be severe enough to trigger the pain buffering response. This is because hospital visits and doctor’s appointments are generally short affairs and they generally involve several social interactions between patient and caregiver (even if these interactions are less meaningful for minority patients). Further, in the case of an extended hospital stay, friends and family may visit the patient and reduce social exclusion caused by communication issues and cultural differences among minorities. With this in mind, it is hypothesized here that social exclusion of ethnic minorities is not typically severe enough to buffer pain, and instead likely enhances it.
When the effect of social exclusion is examined in conjunction with the previously explored effect of low expectations for treatment success, an increase in pain perception by minorities compared to Caucasians is implied. Despite the robust evidence for such a claim, there are several factors that should be considered when examining this hypothesis. For starters, pain is not easily quantified and is involved in a complex web of pathways which undoubtedly interact before a final perception of pain is encoded. For instance, although social and physical pain result in similar patterns of increased neuronal activity, it is conceivable that differing baseline brain activation in each situation could extensively modulate the perception of these different types of pain. Therefore, their added effects may not sum one to one. Building on this, even though pain is associated with increased activation of certain brain areas, these areas are diffuse and the degree to which pain increases with increasing neuronal activity has not been established. Hence, although it is conceivable that increased brain activation and increased pain perception are proportional, a non-linear relationship could also exist between them. On top of this, pain perception involves self-report, which adds noise to experimental results and could be problematic when considering minority patients who may speak different languages that may use different language constructs to represent pain. Finally, this research only examined a small subset of factors that could cause a differing perception of pain by minorities. Although it is feasible that expectancy and social exclusion play a dominating role in the final effect, there are numerous other factors that could play into the result as well.
Despite the potential challenges mentioned in the previous paragraph, the literature reviewed here strongly implicates enhanced pain perception by ethnic minorities compared to their Caucasian counterparts in the United States. The driving force behind such an effect is proposed to be differing expectations and increased social exclusion faced by minorities compared to Caucasians. Further examination of this hypothesis could have direct benefits on pain management, and is highly relevant given that pain is a permeating aspect of many peoples’ lives. Moreover, as the population in America becomes more diverse, this research will become increasingly relevant to providing adequate healthcare to minority groups. Finally, it is important to note that the issues of social exclusion and low expectations about healthcare outcomes are not exclusive to minority groups, so this research could lead to a generalized improvement in healthcare for those who face similar challenges. The reviewed literature suggests that perceived pain could be reduced among minorities if doctors were more clear in their communication about expected pain and if healthcare facilities offered a more inclusive atmosphere to their patients.
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