The classical model of pain, first articulated by the philosopher Descartes in the 17th century, regarded pain as a sensory experience triggered by tissue damage. Despite the fact that this model is unsupported by empirical research, it continues to be a common misconception. Research on pain has demonstrated that it is a complex biopsychosocial phenomenon, with sensory, affective, cognitive, and social components. The International Association for the Study of Pain defines pain as being both a sensory and emotional experience. It goes on to state that pain is always a subjective experience, and its presence cannot be verified by any kind of objective test. Consequently, the only way of knowing if an individual has pain is through the verbal report or other communication of that individual. Chronic pain can sometimes persist in the absence of any identifiable physical cause.
In the acute phase following the onset of disease or injury, pain is often more closely associated with nociception. Nociception is a sensory system that alerts the brain to actual or potential tissue damage and initiates self-protective behaviors. Nociception, however, cannot be equated with pain, as nociception can occur without pain, and pain can occur without nociception. In contrast, as pain becomes chronic, its cognitive, affective, and social components tend to play a progressively larger role. Research studies using functional magnetic resonance imaging (f-MRI) have shown that the brain activity observed while experiencing physical pain is similar to brain activity observed while experiencing social pain or “hurt feelings.” This blurs the distinction between physical and social pain. Similar f-MRI studies have also found that physical pain and imagined pain also produce similar brain activity.
The complex nature of pain has led some to classify pain as being either “real” or “not real,” but this is a false dichotomy. Consider the example of someone whose foot is traumatically amputated in an accident. Many who experience this type of injury will experience “phantom pain,” or pain in the missing foot. Where is this pain? Is this pain “real” and “in the foot”? Or is this pain “not real” and “in the head”? Pain is an inherently subjective experience, and subjectively, this pain is clearly in the foot. Objectively though, there is no foot there to hurt. Consequently, it could be argued that the pain is actually in the stump, where the severed, damaged nerve ending is transmitting the wrong signal to the brain. However, the patient could counter that the pain cannot be in the stump, because the stump itself does not hurt. It could also be argued that the pain is in the brain, because the brain is involved in all subjective experience. The fact that all three of these explanations are correct in their own way illustrates the complex nature of pain. Because all pain is a subjective experience, the individual’s report of pain should be accepted. At the same time, knowing that chronic pain is a complex and multidimensional phenomenon, the various factors influencing pain need to be explored.
Pain and Development
Developmentally, pain is one of the first experiences communicated, when the infant cries in response to painful sensations and draws the attention of care-givers. Thus, from the earliest times of life, pain is experienced in association with emotional distress and is expressed within a social context. It is through these experiences that the child comes to understand the meaning of the word pain, associates sensory and emotional experiences with it, and begins to develop expectancies about what other people will do if pain is experienced.
Within the first few years of life, pain develops into a complex experience. For example, a child who is knocked down by a playful dog and sustains a bruise may cry and complain of pain. Upon closer inspection, however, this child’s report of pain may include unpleasant physical sensations and also a cognitive appraisal of danger, fear of harm, and anger at the dog as well as a desire for the comfort and protection of the parent. If this child’s complaints of pain can be alleviated by a hug and cookie, though, it affirms that this particular experience of pain was not purely sensory information related to tissue damage but was rather an undifferentiated amalgam of unpleasant physical sensations, cognitions, and emotions that was accompanied by a desire for the support of others. In this manner, the perception of pain and its meaning evolves over the course of life.
Most commonly, emotional distress acts to magnify the level of pain caused by organic pain generators. However, a construct that has been used to explain some types of chronic pain is alexithymia (meaning “without words for feelings”). Alexithymia may occur when a person is raised in an emotionally impoverished environment and as a result is unable to express or even recognize emotional states. Such a person, being unable to recognize emotional pain, may be unable to differentiate it from physical pain and may report experiences of both types simply as “pain.” Because medical treatment for physical pain generally does not reduce emotional pain, this can complicate treatment, as it may not be clear what kind of pain is being reported.
Theories of Pain
Modern theories of pain were influenced greatly by Melzack’s gate control theory, which postulated that emotional arousal could alter pain perception by opening and closing perceptual “gates.” Nociceptive information pertaining to pain travels through spinal pathways that take it through areas of the brain known to be associated with affect; limbic structures, the medial thalamic nuclei, and the anterior cingulate play especially important roles. This has led to the use of the phrase limbically augmented pain syndrome to refer to states where chronic pain seems to be closely intertwined with vegetative depressive signs.
One recent theory proposed by Melzack, neuromatrix theory, attempts to explain a variety of pain-related phenomena. The neuromatrix is conceptualized as being a widely distributed neural network in the brain that is in part genetically determined but is also affected by sensory experiences, emotional arousal, chronic stress, and other factors. According to this theory, the neuromatrix interprets nociceptive information and in so doing produces the experience of pain.
Research on stress and the endocrine system by Heim, Bremner, and others helps to shed light on the relationship between chronic pain and chronic stress proposed by neuromatrix theory. For example, patients who report a history of emotionally traumatic events have been found to exhibit increased pituitary-adrenal and autonomic responses to stress compared with controls. This increased reactivity under stress may explain the increased vulnerability to chronic pain that has been observed in those who have suffered emotional traumas.
Pain in the Medical Setting
Research suggests that pain may be the most common single symptom seen by primary care physicians. The National Center for Health Statistics has estimated that up to 80% of office visits to primary care providers involve some complaint of pain, and this accounts for over 35 million new office visits a year. One large study on medical expenditures in managed care found that the medical treatment costs associated with chronic pain exceeded the costs attributable to the treatment of other disorders, such as heart disease, respiratory disease, or cancer. However, unlike these other diseases, which can be diagnosed by objective medical findings, pain is a subjective experience. As a result, the goal of medical treatment for pain is usually to change the verbal report of pain.
Chronic pain can affect any part of the body. However, certain types are more common. In particular, low back pain and headaches are commonly reported. For some types of chronic pain, there is an obvious organic pain generator. However, chronic pain sometimes exceeds what can be explained by objective medical findings and can occur in patterns that cannot be explained on a purely anatomical basis.
The Assessment of Pain
In addition to heart rate, respiration rate, blood pressure, and body temperature, the presence or absence of pain is regarded as one of the five vital signs in medicine. While the other vital signs can be objectively assessed, though, pain cannot. Typically, patients are asked to rate their pain in one of two ways, the first of which involves using a visual analog scale or VAS. On the VAS, pain is assessed by having the patient make a mark on a 10-centimeter long line, where one endpoint is labeled “no pain” and the other endpoint is labeled with some description of extreme pain. Alternately, patients are asked to rate their pain from 0 to 10 using a numerical rating scale or NRS.
The assessment of pain using either the VAS or the NRS is complicated by the fact that these tools are hampered by lack of standardization, which greatly impairs their value. First of all, extreme pain is defined in a variety of ways on these tools. For example, on these measures extreme pain is alternately defined as “the worst pain you can imagine,” “pain so bad you want to die,” or in any number of other ways. However, each of these definitions influences the rating, and a person with moderate pain who was also suicidal might rate pain differently using the two definitions above. Secondly, there are no standardized instructions. For example, these tests have no instruction regarding bodily location of pain, nor do they address the issue of multiple pain sites. Thus, if a patient has a headache of 5 on a 10-point scale and a back ache of 3, it is not clear what number will be reported if the patient is asked simply to “rate your pain level.” When patients have two or more pain complaints, they may alternately pick the highest number, try to average them, or sometimes add them together. Because of this lack of standardization, the numerous variations of the NRS and VAS are not equivalent, and this may influence the results in a variety of ways. As a result, while the other vital signs all have agreed-upon means of assessment and cutoffs for what is high, pain has neither.
More recently, new assessment tools have been developed that have attempted to address this problem. In particular, the Battery for Health Improvement 2 (BHI 2) is the first test to offer a multidimensional assessment of chronic pain with standardized instructions and established validity and reliability. The BHI 2 assesses pain in multiple locations, overall pain, pain variability over time, pain tolerability, and pain-related cognitions. These pain reports can be compared to national norms for both community members and medical patients and also to patients in the same diagnostic category. Further, this instrument also includes a variety of other scales that assess the biopsychosocial context in which the pain occurs.
Because chronic pain is a biopsychosocial phenomenon, treatment for pain optimally involves a multidisciplinary team that addresses pain’s biological, psychological, and social components. The biological aspects of chronic pain are addressed by physicians whose task is to evaluate the patient and identify any injury or disease that may be contributing to the pain experience. Treatment may involve a variety of medications, including medications for pain or inflammation as well as medications specific to any disease that may be present. Antidepressant medication may be prescribed to help with associated affective distress. Additionally, though, as pain and affect are closely related, some antidepressant medications also have an analgesic effect. Medications may be prescribed for insomnia, which is frequently seen in patients with chronic pain. Medical treatment can also involve surgery, injections, and other invasive procedures. Lastly, the physician may refer the patient for physical therapy as well.
The psychosocial aspects of chronic pain are usually treated by mental health professionals who can help patients with chronic pain in several different ways. First of all, psychological treatment has commonly been used to help patients manage their pain. However, more recent research has shown that psychological treatment can significantly reduce pain as well. Counseling the individual with chronic pain may involve helping this person to develop better techniques for pain management. Individuals with chronic pain sometimes “catastrophize” and view their situation as being worse than objectively is the case. Individuals with chronic pain can also become somatically preoccupied. This preoccupation with pain may heighten the pain experience and increase the level of affective distress and suffering. Catastrophizing and somatic preoccupation can lead an individual with chronic pain to feel extremely fragile, and this can lead to excessive self-limiting behaviors out of an irrational fear of self-harm. This self-limiting behavior can in turn lead to a progressive physical deconditioning and to further disability. Helpful techniques involve teaching the patient to shift attention away from the pain, to develop a more realistic appraisal of the pain and any associated disability, and to identify desirable activities that the individual should continue to engage in.
The onset of chronic pain may require the patient to make a multitude of lifestyle changes. Patients with chronic pain can often benefit from the opportunity to discuss all of these new life challenges with a mental health professional and from using a problem-solving approach to address whatever changes are necessary in work, home responsibilities, hobbies, and other activities.
Because chronic pain and any associated disability can be stressful, offering the patient stress management techniques is often helpful. This may include relaxation training or biofeedback. Stress management is important, because stress tends to increase physiological arousal levels. As noted above in gate control theory, physiological arousal tends to increase the experienced intensity of pain. This can lead to an ever-worsening syndrome, where pain leads to stress, and the stress heightens the pain experience, which then in turn worsens the stress. It should also be noted that some types of chronic pain, such as chronic tension headaches, can be produced entirely by stress.
Chronic pain is also commonly associated with depression, anxiety, and anger. Individuals with chronic pain may feel despondent or angry about having to constantly cope with pain and may be fearful about the future. As with stress, strong emotions also tend to increase the level of experienced pain. The term suffering is sometimes used to refer to the combination of pain and emotional distress that is felt. Helping the individual with chronic pain to reduce the level of emotional distress will reduce the level of suffering and may reduce the level of pain as well.
Chronic pain is often associated with insomnia, as the patient cannot get comfortable and also may be too distressed to sleep. In addition to stress management training, there are specific techniques for insomnia control that are sometimes referred to as sleep hygiene training. Research has shown that these techniques are about as effective as medication for treating insomnia. Additionally, unlike medications, these techniques have no side effects.
When an individual suffers from chronic pain, it may have an impact on the entire family. The individual with chronic pain may no longer be able to take care of his or her usual household responsibilities, and this may be very disruptive. While a healthy family will tend to rally behind the individual with chronic pain, the dysfunctional, unsupportive family may refuse to adjust to the chronic pain condition. This may increase the emotional distress of the individual with chronic pain and force the individual to perform activities that worsen the pain. On the other hand, overly supportive families may encourage the individual with pain to adopt a passive role, which in turn may only increase disability. The quality of life of the individual with chronic pain can improve considerably if the family can learn to provide the optimal level of support.
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