The Relationship Between Different Exposures of Pain Stimuli and Development of Pain Tolerance

Abstract

Pain is a physiological response that our body uses to alarm us of any dangerous stimuli, but it has been found that pain goes beyond just a physiological response. Studies have provided inconclusive findings on the environmental factors at play in the development of an individuals nociceptive processing. The difference of an undesirable painful stimulus against a desirable one may greatly contribute to the overall development of pain tolerance and the intensity that is felt during a painful stimulus. Knowing a patients history with painful stimuli can provide crucial insight into the behaviors before and after a treatment. It will also provide a better understanding of the relationship between the physiological and psychological makings of the nociceptive system. This is a quantitative and correlational study design. Participants will be recruited from the university and surrounding neighborhoods. Subjects will complete multiple questionnaires, test, and tasks to determine the relationship between painful environmental stimulus and the development of the psychological pain. The Revised Reducer-Augmenter Scale (RRAS) and the Trauma History Questionnaire (THQ) will be administered to measure preferred stimuli and past traumatic experiences. A Cold Pressure Task (CPT) will be administered to measure the tolerance and intensity of pain for each individual. The results of this proposal are yet to be determined. It is the aim that the results of this study will provide more information on the development between physiological and psychological processes of pain.

Introduction

The ability to feel pain goes far beyond nociception and the nervous system. Humans share an identical physical process of pain, but there are psychological differences. Evidence suggests that pain perception is molded by many factors, such as genetics and environmental stressors (Croy et al. 2011). These overlap with one another to create the individual differences in people’s pain tolerance. Few studies have been done to address these differences in individuals.

There are many ways to experience a painful stimulation. Traumatic painful stimuli throughout the course of a lifetime will be felt differently than experienced pain stimuli through encouraged activities. The neurological understanding of pain has been extensively studied and is well understood throughout the scientific world. Little research has been done on the development of pain tolerance. It lacks the consideration that not all pain is the same. The study supports the theory that not all painful stimuli is psychologically processed the same. It is hypothesized that pain experienced with fear and anxiety will result in a lowered pain tolerance (Rhudy & Meagher, 1999): in comparison to accepted pain, increasing pain tolerance. This pain can provide information to develop more individualized care for those who will experience painful situations. This study aims to further investigate the relationship different exposures of painful stimuli have on the development of pain tolerance.

Literature Review

Psychological and biological factors work together to shape the way humans perceive pain. Creating categorical constructs, such as desirable and undesirable experiences, of pain can provide a vast amount of literature and theories that explain how and why humans perceive pain differently from one another. Pain is both objective, within the nervous system, and subjective, varying in perception from person to person. Nature and nurture work together to impact human’s perception of pain, this review will focus on research that supports four topics of significant interest. An abundant amount of research suggests that factors such as genetics, fear and anxiety, cultural norms, and personality all contribute to these key differences. Pain perception includes a variety of concepts of pain, but this review will focus primarily on pain tolerance.

A human’s genetic make-up includes an exceptional amount of information and the expression of certain genes may adjust according to the environmental surroundings of a person (Croy et al. 2011). When experiencing a fear-inducing situation, the nervous system tends to slow signaling to the pain center, suppressing the painful stimulus. When the body is under stress, the fight or flight system is activated creating an analgesia effect (Rhudy, 2000). To escape a dangerous situation without being distracted by pain is a survival instinct. The biological numbing of the pain in correlation with the experience of fear may have an effect on people’s tolerance of pain in the future. It would benefit the field to further examine these differences in pain with each fearful experience.

Anxiety and fear work together to induce an appropriate response to painful or dangerous situations. It is a survival tactic that effects humans even when a situation may not be necessarily dangerous, but uncomfortable. For example, research shows that children experiencing anxiety when receiving medical attention have a lower pain tolerance than those who are distracted (Nilsson et al. 2013). Something as simple as distraction from pain changes how humans perceive to feel it. When the children are distracted from the anxiety of the medical care, it is shown that the tolerance for pain is higher than those who do not have the distraction from anxiety and medical care. Croy’s (et al., 2011) study used interactive games as the distraction while the children received medical treatment. The study examined the importance of active distraction versus passive distraction by instructing one group to play a video game, another group given a less interesting distraction; the control group was not given any distraction.

It is widely understood that personality is an important contributing factor when experiencing stimulation. Schwedtfeger (2007) has studied two distinct personality traits that serve as a probable predictor of how an individual will tolerate pain. These traits are known as augmenting and reducing behaviors. Augmenters will exhibit behavior that avoids painful stimuli, resulting in a weakened tolerance to pain; for example people avoiding dental work or limping to accommodate a foot injury. Reducers will mitigate painful stimuli, resulting in an increased ability to tolerate pain. Reducers are more likely to participate in contact sports or activities that may lead to possible injury for excitable stimulation. In a lifetime they are more likely to have more painful experiences, than reducers, who limit their exposure to painful stimuli.

Environmental factors can influence these fears and anxieties through many channels. Societal customs and demands play an important role in people’s perception of pain. Expectations to handle pain are different amongst gender, age, and cultures. These differences can only be learned through social experience and interaction. Gender differences have been of great interest and the numerous amount of research suggests there is a significant difference in the perception of pain between men and women (Robinson et al., 2003). Findings indicate men have a higher pain tolerance compared to women when experiencing a painful stimulus. This may be because of societies expectation of men to express less when experiencing pain to maintain ‘manliness’. So, when men are faced with painful stimuli, they are expected to internalize that painful experience. Women on the other hand, are not expected to handle pain the same way. Expressing and not tolerating pain is what is expected, creating a difference in pain tolerance.

Cultural differences have an impact on reactions to painful stimuli as well. The expression to pain specifically is dependent on societal norms, beliefs, and values. Studies support a significant difference between western and eastern culture’s expression and tolerance to pain. Although gender seems to have a collective influence around the globe, eastern countries show a higher tolerance and a lower reaction, or expression, to pain. Cultural expectations and rituals are believed to contribute to these findings. The rituals that are preformed from childhood through adulthood induce painful stimulus. The exposure and expectation to follow through with these rituals force an individual to find their own way to cope with the pain personally to avoid cultural isolation (Belfer, 2013). In contrast, western countries, such as the United States, accept expression of painful stimuli verbally and nonverbally. The culture is conditioned to medicate even the slightest discomfort, exposing the population to fewer and shorter painful situations. In likeness to the differences between males and females, eastern cultures are expected to withstand more pain to satisfy religious and cultural beliefs. Western countries do not hold these same beliefs of practices, which result in less exposure to pain and lower acceptance of pain.

Prior exposure to painful situations may cause protected behavior or unprotected behavior (Linton et al. 2016). One may avoid a certain activity or have negative thoughts repeating in their head, like “this is going to hurt terribly”, increasing pain and lowering tolerance. Anticipation of a painful stimulation provokes already perceived expectations of that stimulation. For example, a needle is known to inflict pain, which causes anxiety or fear and will often result in a lower tolerance to pain in general. Others may seek more stimulating activities, like individuals that engage in tattoo art, therefore increasing tolerance. Some research suggests that experience with pain increases pain tolerance (Tajet-Foxell & Rose, 1995), while others provide the opposite suggesting prior exposure to pain will result in a lower tolerance. Little research has classified painful stimulation as multidimensional. Typically there is one measurement of pain and multiple behavioral manipulations. The idea of ‘different’ painful stimuli in relation to the on the development of pain sensation, specifically tolerance, has yet to be examined. This study distinguishes two of those differences, classifying them as painful stimulation that is desirable, stimulation that is accepted and sought after, or undesirable, stimulation that has been forced upon and traumatic. It is hypothesized that desirable painful stimuli will result in an increased tolerance, in contrast to undesirable painful stimuli resulting in a decrease in tolerance. This study examines the relationship between desirable and undesirable painful stimuli and pain tolerance.

Methods

Participants

It is anticipated that this study will include between 90 to 100 participants, both males and females are accepted. Recruitment will be done through posted advertisement on a campus and the surrounding neighborhood spanning a 1-mile radius. Two different rewards will be offered as incentive to participate. Any participants that are students will receive one credit per session, towards a university requirement. Local participants will be rewarded one $25.00 gift card per session, to a local café. The accepted age range is 18-32 years old, with the expected mean of 23 years. Considering the diversity of both the university and neighborhood, it is anticipated to have participants representative of American-Hispanics, Caucasian, and African-American.

Measures

The revised version of Vando’s Reducer-Augmenter Scale (RRAS) by Rock Clapper (1990) was used to identify specific behavioral traits in participants. This is a self-report questionnaire that can measure the preferred stimulation that will elicit a response from the central nervous system. It has also demonstrated predictions of person’s participation in high or low risk behaviors. It is a 21-item questionnaire with a six-point scale, measuring between two types of stimulation, high and low. Two listed events or feelings, such as “be with a crowed” and “be alone” are presented with the scale. Low-risk behavior is rated at a value of 6 and high-risk behavior rated at the value of 1. Final scores will address two traits, being reducers or augmenters. Reducers prefer high stimulating experiences and augmenters prefer low stimulating experiences. When calculating, the scale is flipped and the summed scores for augmenters will be represented by low totals and reducers will be represented by high totals. For the purpose of this study, cut off scores were distinguished between low and high, without a medium measurement. This means the cut off score to determine augmenter or reducer will be evenly split in half. Participants that have a total score of 63 and below will be labeled as ‘augmenters’. Those with totals of 64 and above will be labeled as ‘reducers’. In testing validity and reliability, there was high correlation with comparable constructs from other studies and consistency amongst test takers in both high school and college. This scale is being used to measure the participant’s preferences of external stimulation.

The General Activity Survey is a 42-item survey prepared by the author. The validity and reliability of this questionnaire is not yet known. This is the first time it is being used. It is the aim to examine each participant’s past exposures, or lack there of, to different activities that do and do not stimulate painful stimuli through a variety of activities. Each activity is listed with a 5-point Likert-Scale, rating the likability of each activity from “strongly agree” to “strongly disagree”. For example, the participant is instructed to indicate the degree of agreement to a statement like “You enjoy receiving tattoos” and “Activities you participate in often result in bruises”. There are 4 subscale measurements within this questionnaire demonstrating exposures to (a) strenuous physical performances (9 items), (b) low impact (8 items), (c) high impact (13 items), and (d) no impact or strain (11 items) experiences. Included is a final (1) item offered as self-report on anything that was not covered in any of the other items. Whether this item is counted in the total is up to the discretion of the investigator. There is a total score between 0 and 210. Participants with low scores are considered as subjects that have “low exposure” to painful stimuli in contrast with those that scored high expressing “high exposure” to painful stimuli.

A Trauma History Questionnaire (Hooper, 2011) is a 24-item trauma history questionnaire. It is a self-report instrument to gather reliable information of the individuals ‘lifetime exposure to diverse traumatic experiences’. Questions asked sound something like “Has anyone ever tried to take something directly from you by using force or the threat of force, such as a stick-up or mugging” or “Have you ever had a serious accident at work, in a car, or somewhere else”? The total score may fall between 0 and 24, with a subscale reflecting traumatic events such as (a) crime related events (4 items), (b) general disaster and traumatic experiences (13 items), and (c) physical and sexual trauma (6 items). The last item is provided as a self-report that may not be covered and is up to the discretion of the investigator to include or not. Low scoring participants were labeled as those who have had a “low magnitude” of trauma. High scoring participants were labeled as those who have had a “high magnitude” of trauma.

To put the hypotheses to the test, the Cold Pressor Task will be used to measure the nociceptive stimulus intensity and tolerance. It is a standard laboratory technique often used to measure subjects’ pain tolerance thresholds. An 8” by 8” tank was used to hold water. The water was kept at 4°C using two tubes to continuously circulate the water to ensure consistent temperature. A total of three thermometers were placed in the tank to ensure the temperature stayed the same throughout the trials. All thermometers were checked once before starting and once after the trail as ended. To ensure that all participants had the same starting point, the left hand was placed in a tank with 37°C water for 2 minutes. Participants used a 5-point Verbal Rating Scale (VRS-5) was used to indicate that intensity of the pain every 30 seconds throughout the duration of the trial. The time of extraction of the hand from the cold water/ was recorded with the last indicated intensity.

Procedures

All participants will be subject to two sessions consisting of multiple tests and questionnaires. On arrival students were briefed on the purpose of this study, the tasks that will be preformed, and informed that they had the ability to leave the study at any point in time. The first credit was given to students and the first gift card was given to non-students. Immediately after, they were asked to indicate whether they were a high school or collegiate athlete or non-athlete. The first session is expected to run about 90 to 120 minutes that will include the Revised Reducer-Augmenter Scale (RRAS) test and the General Activity Survey (GAS). Participants will be placed in a plain conference room with the test and a pencil. It was instructed that the test was not timed and to answer the questions as honest as possible. The RRAS test was distributed first followed by the GAS. Participants were given a 10-minute break between the test and survey. After completing both the test and survey and another 10-minute break, the first trial of CPT was administered. To establish a baseline the participants were instructed to place their non-dominant hand in a bucket of water at 37°C for 2 minutes. Directly from the bucket, they put the same hand into the 4°C tank for as long as they can stand, not exceeding 5 minutes. Every 30 seconds they were asked to report verbally based on the 5-point Likert-Scale. The time of extraction was recorded along with the last rated intensity. Participants were debriefed and asked to return exactly two weeks after for the second session. The second session comprised of the THQ and the CPT. This session is expected to go for about 60 to 90 minutes. The trauma questionnaire will be distributed before the second trial of the cold pressor task. Participants will be taken into the same office space as the week before, given a pencil, and read the same instructions from the prior session. A 10-minute break is given before starting the second trial for the CPT. Procedures will stay the same as the first session. After the completion of the second session, the second credit for students and gift cards for non-students will be distributed.

Results: Results are yet to be Determined

Discussion

The aim of this study is to examine the relationship different exposures of pain have on the development of pain tolerance. It is expected that those who have faced traumatic experiences involving painful stimuli will score lower on the RAS and the questionnaires. They will also report a lower threshold and higher intensity to the Cold Pressor Task (CPT). Alternatively, those who have participated or experienced desirable pain stimuli will score high on RAS and the provided questionnaires. The testing will show that these individuals will report a higher tolerance and lower intensity ratings.

Research has suggested that pain is an experience greater than just an alarm of dangerous stimuli. Acknowledging differences in painful stimuli will further address differences between people’s tolerance to painful stimulation. It will be shown that people who participate in desirable experiences that include painful stimulation will typically develop a higher tolerance. It was found that children who engage in self-injury show an increased tolerance to pain, even after a year of reduction or terminated behavior. Another study showed an athlete’s training and participation will typically follow this pattern of increased tolerance because of the consistent exposure to painful stimulation. This can entail impact during play, soreness of muscles, or both at the same time increasing exposure and duration of exposure. Both of these studies focus on behaviors that are desirable, but still stimulate pain.

Alternatively, undesirable experiences will develop low tolerance. For example, child abuse and other types of abuse during childhood or even adulthood may result in sensitivity to pain, therefore a lower tolerance. This exposure to painful stimulation is not considered as desirable experiences, therefore not accepted amongst those who are experiencing it. A study conducted by Ana Masedo and her collogues (2006) found that ‘accepting’ pain will increase a person’s tolerance. An undesirable experience is painful stimulation that was forced upon rather than sought after. This may be a key difference in development.

It is beneficial to use a correlational design to measure due to the fact that it is unethical to orchestrate traumatic experiences in a lab setting. This type of study cannot offer cause and effect, but instead will further support and provide more information into the psychological dimension of pain processing. It will provide data that a relationship between desirable or undesirable pain and tolerance exists. The Reducer-Augmenter Scale has been used to measure personality dimensions on both children and adults in clinical settings (Schwerdtfeger, 2007). Also, the Trauma History Questionnaire measures the severity and extent of experienced trauma. These measurements strengthen the subjective construct of behaviors that is considered desirable and painful, and undesirable and painful. It also improves the internal validity of the experiment by allowing accurate measurement of the subjective construct. The General Activity Questionnaire has yet to be validated or tested for reliability, posing a threat to the internal validity of this study. Further studies testing its reliability must be conducted.

This study does not include a mental health screening or a psychological evaluation for underlying mental issues, which may have an affect on ones perception of painful stimulation. Further research may include this in exclusion criteria to increase the internal validity. This will also allow an increase external validity when improving pain therapies. The questionnaires being self-report create a threat to internal reliability, as reports may be inconsistent. Trauma is a personal experience that may not be entirely truthful in a self-report. Some may exaggerate experiences and other may understate the experiences. Lastly, The possibility for a lack of diversity to reflect the general population will also harm this studies external validity.

Supplementary evidence for psychological processes of pain will have many benefits in both psychological therapies and medical therapies impacting pain. This study in particular will develop an understanding of behavior in response to pain depending on prior experiences. This can be vital to practices involving post surgeries, or those who experience extraneous circumstances such as the phenomena phantom limb. This study also creates a dimension of painful stimulation, pin pointing a difference in felt pain. Further research should also consider different expressed genes in relation to the type of painful stimuli. This can further specify to what degree the environment influences a human’s pain tolerance.

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