Limitations of Pharmacotherapy: Behavioral Approaches to Chronic Pain
Abstract Pharmacotherapy is most appropriate in acute pain, whereas in chronic pain states behavioral approaches or a combination of behavioral treatment and pharmacotherapy is more appropriate. In this chapter we ﬁrst describe the role of learning and memory as well as other psychological factors in the development of chronic pain and emphasize that chronic pain must viewed as the result of a learning process with resulting central neuroplastic changes. We then describe operant behavioral and cognitive-behavioral treatments as well as biofeedback and relaxation techniques and present innovative treatment procedures aimed at altering central pain memories. We complete the section with a discussion of combined behavioral and pharmacological approaches and an interdisciplinary view.
Keywords Operant conditioning in acute and chronic pain · Learning · Memory · Physical training · Cognitive and behavioral therapeutic approaches · Multidisciplinary rehabilitation
Pharmacotherapy of chronic pain has several limitations. First, the drug does not always target the region in the central nervous system where the main effect should be but will occupy all receptors, thus leading to unwanted general and side effects. Second, analgesic medication is as much prone to tolerance and loss of efﬁcacy as other drugs, and especially opioids can themselves induce hyperalgesia over time (Angst and Clark 2006). Third, long-term analgesic medication can be associated with learning processes that enhance the amount of medication consumed and can drive patients into dependence and lead to cognitive and other neuropsychological deﬁcits (Buntin-Mushock et al. 2005). Moreover, in chronic states of pain the initial cause of the pain is often no longer relevant and other—in many cases central—factors may now be causal for the pain that is experienced. In this chapter we will give an overview of the behavioral and learning-related factors that contribute to chronic pain, including their neural correlates, and will then describe behavioral as well as combined behavioral and pharmacological approaches that can address these factors and can overcome some of the limitations of pharmacotherapy.
The Role of Learning Mechanisms and Psychological Factors in Chronic Pain
A new era in thinking about pain began with Fordyce’s (1976) description of the role of operant factors in chronic pain. In the operant formulation, behavioral manifestations of pain rather than pain per se are central. It is suggested that when an individual is exposed to a stimulus that causes tissue damage, the immediate response is withdrawal and attempts to escape from noxious sensations. This may be accomplished by avoidance of activity believed to cause or exacerbate pain, help seeking to reduce symptoms, and so forth. These behaviors are observable and, consequently, subject to the principles of operant conditioning, i.e., they respond to contingencies of reward and punishment.
The operant view proposes that acute “pain behavior” such as limping to protect a wounded limb from producing additional nociceptive input may
come under the control of external contingencies of reinforcement and thus develop into a chronic pain problem. Pain behavior (e.g., complaining, inac- tivity) may be positively reinforced directly, for example, by attention form
a spouse or healthcare provider. Pain behavior may also be maintained by the escape from noxious stimulation by the use of drugs or rest, or the avoidance
of undesirable activities such as work. In addition, “well behavior” (e.g., ac- tivity, working) may not be sufﬁciently reinforcing and the more rewarding pain behaviors may therefore be maintained. The pain behavior originally elicited by organic factors may come to occur, totally or in part, in response to reinforcing environmental events. Because of the consequences of speciﬁc behavioral responses, it is proposed that pain behaviors may persist long after the initial cause of the pain is resolved or greatly reduced. The operant con- ditioning model does not concern itself with the initial cause of pain. Rather it considers pain as an internal subjective experience that may be maintained even after an initial physical basis of pain has resolved. Operant conditioning can lead to increased inactivity and invalidity and also plays an important role in the increase of medication levels since the intake of medication—especially on a prn basis when there are high pain levels—may be viewed as a conse- quence of a negative reinforcement process (a negative consequence, the pain, is removed by medication intake). Not only observable pain behaviors but also verbal expressions of pain and physiological variables may come under the control of the contingencies of reinforcement.
Respondent Learning Mechanisms
Factors contributing to chronicity that have previously been conceptualized in terms of operant learning may also be initiated and maintained by respondent conditioning (Gentry and Bernal 1977). In the typical classical condition- ing paradigm, a previously neutral variable (conditioned stimulus, CS), when paired with a biologically signiﬁcant stimulus (unconditioned stimulus, US) comes to elicit a conditioned response (CR) that resembles the response to the unconditioned stimulus, the unconditioned response (UR). For example, if a certain movement has been associated with pain, just thinking about the movement may already elicit fear and muscle tension (previously elicited by pain) and may then motivate avoidance behaviors. Lethem et al. (1983) have suggested that once an acute pain problem exists, fear of motor activities that the patient expects to result in pain may develop and motivate avoidance of activity. Nonoccurrence of pain is a powerful reinforcer for reduction of ac- tivity and thus the original respondent conditioning may be followed by an operant learning process whereby the nociceptive stimuli and the associated responses need no longer be present for the avoidance behavior to occur. In acute pain states it may be useful to reduce movement, and consequently avoid- ing pain, to accelerate the healing process. Pain related to sustained muscle contractions might, however, also be conceptualized as a US in the case where no acute injury was present and sympathetic activation and tension increases might be viewed as URs that may elicit more pain, and conditioning might proceed in the same fashion as outlined above. Thus, although the original association between pain and pain-related stimuli results in anxiety regarding
these stimuli, with time the expectation of pain related to activity may lead to avoidance of adaptive behaviors even if the nociceptive stimuli and the related sympathetic activation are no longer present. Fear of pain and activity may become conditioned to an expanding number of situations. Avoided activi- ties may involve simple motor behaviors, but also work, leisure, and sexual activity. In addition to the avoidance learning, pain may be exacerbated and maintained in these encounters with potentially pain-increasing situations due to the anxiety-related sympathetic activation and muscle tension increases that may occur in anticipation of pain and also as a consequence of pain. Thus, psychological factors may directly affect nociceptive stimulation and need not be viewed as only reactions to pain. Vlaeyen and Linton (2000) have shown that fear avoidance is a major predictor of chronic pain and disability.
Cognitive Factors in Chronic Pain
Cognitive-behavioral models of chronic pain emphasize that the evaluation of the pain experience by the patient greatly determines the amount of pain that is experienced as well as its negative consequences (Turk et al. 1983). Gen- eral assumptions that characterize the cognitive-behavioral perspective are: (1) people are active processors of information and not passive reactors; (2) thoughts (e.g., appraisals, expectancies) can elicit or modulate mood, affect physiological processes, inﬂuence the environment, and serve as the impetus for behavior. Conversely, mood, physiology, environmental factors, and behav- ior can inﬂuence thought processes; (3) behavior is reciprocally determined by the person and environmental factors; (4) people can learn more adaptive ways of thinking, feeling, and behaving; and (5) people are capable and should be involved as active agents in change of maladaptive thoughts, feelings, and behaviors.
From the cognitive-behavioral perspective, people suffering from chronic pain are viewed as having negative expectations about their own ability to con- trol certain motor skills such as performing speciﬁc physical activities (e.g.,
climbing stairs, lifting objects) that are attributed to one overwhelming fac- tor, namely, a chronic pain syndrome. Moreover, chronic pain patients tend to believe that they have a limited ability to exert any control over their pain.
Such negative, maladaptive appraisals about the situation and personal efﬁcacy may reinforce the experience of demoralization, inactivity, and overreaction to nociceptive stimulation. A great deal of research has been directed toward
identifying cognitive factors that contribute to pain and disability. These have consistently demonstrated that patients’ attitudes, beliefs, expectancies about their plight, themselves, their coping resources and the healthcare system affect their reports of pain, activity, disability, and response to treatment. A num-
ber of studies have used experimental pain stimuli and demonstrated that the conviction of personal control can ameliorate the experience of experimen-
tally induced nociception. Moreover, the type of thoughts employed during exposure to painful stimulation has been related to pain tolerance and pain intensity ratings. Catastrophic thoughts have been associated with lower pain tolerance and higher ratings of pain intensity. In contrast, coping thoughts have been related to higher pain tolerance and lower pain intensity ratings. Once beliefs and expectancies (cognitive schemata) about a disease are formed they become stable and are very difﬁcult to modify. Patients tend to avoid ex- periences that could invalidate their beliefs and they guide their behavior in accordance with these beliefs even in situations where the belief is no longer valid (no corrective feedback is received to discredit this belief ). For example, feeling some muscular pain following activity may be caused by lack of mus- cle strength and general deconditioning and not by additional tissue damage. Imaging studies have shown that cognitive factors modify the central process- ing of pain and that attention can increase and distraction can decrease brain activation related to pain.
Pain and Affect
The affective factors associated with pain include many different emotions, but they are primarily negative in quality. Anxiety and depression have received the greatest amount of attention in chronic pain patients; however, anger has recently received considerable interest as an important emotion in chronic pain patients. Research suggests that from 40% to 50% of chronic pain patients suffer from depression (Bair et al 2003). There have been extensive and fruitless debates concerning the causal relationship between depression and pain. In the majority of cases, depression appears to be the patients’ reaction to their plight. The presence of depression is closely related to the feelings of loss of control and helplessness often associated with pain. Several investigators have also found a close association between fear of pain and dysfunctional coping. In addition, high comorbidity between anxiety disorders and pain seems to be present. Muscular hyperreactivity to stress seems to be closely associated with fear of pain. Anger has been widely observed in individuals with chronic pain. The internalization of angry feelings seems to be strongly related to measures of pain intensity, perceived interference, and reported frequency of pain behaviors. Anger and hostility are closely associated with pain in persons with lower back pain. Frustrations related to persistence of symptoms, limited information on etiology, and repeated treatment failures along with anger toward employers, the insurance industry, the healthcare system, family members, and themselves, also contribute to the general dysphoric mood of these patients. The impact of anger and frustration on exacerbation of pain and treatment acceptance has not received adequate attention. It would be reasonable to expect that the presence of anger may serve as an aggravating factor, associated with increasing autonomic arousal and blocking motivation
and acceptance of treatments oriented toward rehabilitation and disability management rather than cure, which are often the only treatments available for chronic pain.