determinants of pain behaviour in patients with chronic low back pain
TRANSCRIPT
Determinants of Pain Behaviour in Patients with Chronic Low Back Pain
An n-M ari Es t I an de r
Experience of pain is manifested by a subject’s behaviour, i.e. by verbalisation, move- ments, facial expressions etc. Experience of pain is a latent consfruct, and the ques. tion of whether the pain is “real” becomes secondary when the behavioural aspect is emphasised: “When the patient communicates pain, then there is a pain problem”. The task of the clinician and the researcher is to find out what is behind a person’s response to pain. The pain behaviour is determined by many factors. These include psychologi- cal suffering due to emotional distress; learning processes regulating pain behaviour; anticipated pain and fear of pain as a cause of passivity and avoidance behaviour in chronic low pack pain patients; the influence of cognitive factors, particularly the rela- tionship between negative expectations, cognitive distortion and activity; and finally, the role of psychological distress in chronic pain. These factors are discussed in this paper. Some empirical studies are briefly reviewed to illustrate the topic. Implication of these conceptualisations for treatment of and outcome research in chronic low back pain wi l l be briefly discussed.
Key words: pain behaviour; low back pain.
(Annals of Medicine 21: 381 -385, 1989)
Introduction
During the past decade, increasing emphasis has been put on the psychological aspects of chronic pain e.g., the behavioural, cognitive and affective aspects. W. Fordyce, one of the first people to analyse chronic pain from a behavioural perspective made an important ad- dition to Merskey’s (1) definition of pain, emphasising the behavioural aspect: “Pain is an unpleasant ex- perience associated with actual or potential tissue damage or described in terms of tissue damage or both and the presence of which i s signalled by some form of visible or audible behaviour” (2). In clinical pain, suffering becomes an issue because it leads to pain behaviours.
Pain Experience and Pain Behaviour
The word pain has, somewhat loosely, been used to de- scribe the sensory experience of pain, the psycholog- ical suffering related to pain and sometimes also psy- chological suffering unrelated to a nociceptive pain ex-
From the Rehabilitation Foundation, Helsinki, Finland. Address: Ann-Mari Estlander, MSc., Rehabilitation Foun-
Received: April 11, 1989. dation, Pakarituvantie 4, SF-00410 Helsinki, Finland.
perience. A distinction between the concepts pain be- haviour and pain experience serves to clarify the sub- ject. Suffering and pain are manifested and identified by some form of behaviour: the patient communicates his distress and his pain experience through non-ver- bal or verbal responses.
Pain behaviour, according to Fordyce (Z) , include ver- bal complaints, non-verbal sounds, postures, move- ments, facial expressions, and behaviour to reduce pain (rest, medication) etc. The sensory experience, pain, in itself is a purely subjective, latent construct, which can be estimated or assessed only through the patient’s behaviour. The reliance on patient reports in evaluating pain is reflected in the IASP (International Association for the Study of Pain) taxonomy: patients’ self-reports of pain intensity and quality, of temporal characteristics and pattern of symptoms etc. serve as the basis for classifying chronic pain (3).
Pain as a Complex, Multimodal Phenomenon
Pain is not just a sensory experience that can be cor- related with organic findings; it is a complex phenome- non also involving physiological, behavioural, emotion- al and cognitive factors (2, 4). This conceptualisation implies a multifactorial model of illness and disability instead of an eitherlor explanation. Patients with
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chronic low back pain (CLBP) may have psychosocial or psychophysiological factors contributing to the problem, in the presence or absence of abnormal phys- ical findings (4, 5).
With this conceptualisation of chronic pain, the start- ing point in clinical work and research should be: when a patient communicates pain, there is a pain problem. Our task is to unravel the factors influencing this com- munication, the pain behaviour.
Determinants of Pain Behaviour
Pain behaviour is regulated by various factors. Some specific pain behaviours are more often observed in one type of patient than in another. Some, e.g., limp- ing, are probably a function of organic pathology. Oth- er behaviour, e.g. grimacing, is an innate expression while other behaviour, e.g. protectiveness and passivity can be learned responses to prevent (.anticipated) pain (6).
This paper presents, a slightly revised model by For- dyce (2) describing factors influencing pain behaviour in an attempt to analyse and explain some of these fac- tors and their interactions (Table 1). The model is hypothetical, but some empirical evidence supporting certain aspects of it will be given. The various factors described in this model are not mutually exclusive. There is a continuous reciprocity between them, and probably in most cases many of these factors simul- taneously regulate the behaviour of the individual pa- tient.
Nociception
Nociception is when a pathogenic factor continues to cause respondent pain. Nociception leads to pain and to suffering, which in turn leads to pain behaviour. The difficult issue of the relations between nociception and chronic low back pain will not de discussed here.
Table 1. Factors influencing pain behaviour. ~~
Source Explanation
Nociception Mislabelled suffering
Learning processes
Cognitive d I s t ort ion
Affective distress
An active pathogenic factor causing pain. Psychological suffering caused by situa- tional or emotional distress is interpreted by the patient as pain or behaviour com- municating psychological suffering is in- terpreted by the environment as due to pain. Learning factors regulate pain experience and pain behaviour: A. Respondent conditioning of anxiety and tension B. Operant conditioning of “pain be- haviours” by direct or indirect reinforce- ment or by punishment of “well be- haviours”. Cognitive appraisal (anticipation, atti- tudes, beliefs etc.) influencing behaviour and affective reactions. Depression, fear, anxiety, irritation etc.
Suffering Labelled as Pain
Suffering means undergoing or experiencing pain, loss, grief, defeat, change, punishment, wrong etc. (7). Thus, pain is just one out of several causes of human suffer- ing. Pain and suffering are not identical phenomena. The degree of pain is not necessarily related to the de- gree of suffering, and suffering can occur in the ab- sence of pain. Sometimes, the experience of suffering due to psychological or situational factors may be ex- perienced or interpreted by the individual as pain. Or, others may mistakenly attribute the suffering person’s behaviour to physical nociception (2).
Learning Processes Regulating Pain
An individual’s responses to pain are influenced by the environment and by learning mechanisms. The develop- ment of a chronic low back problem takes time and so the opportunities for learning are many. Fordyce (2,8) has pointed out the importance of learning processes in the development and maintenance of pain behaviour. Two of these learning processes are briefly discussed here.
1. Respondent conditioning of fear and tension. Respondent conditioning is a potent conditioning proc- ess, especially in the acute phase, but it also plays an important role later throughout the course of the pain problem. An acute injury, e.g., muscle sprain due to lift- ing in a specific situation, leads to fear, anxiety and muscle tension. “It hurt last time I lifted, it will hurt this time too”. By time, the situation-related fear and anxiety causes muscle tension and, under certain con- ditions, pain (9, 10).
2. Operant conditioning of pain behaviour. Operant conditioning is said to take place when contingencies in the environment reinforce behaviour. The postulate “positive reinforcement” states that the occurence of pain behaviour will increase in frequency i f it is fol- lowed by positive consequences. “When I show them that I have pain, “good” things happen which otherwise would not”. Examples of these positive reinforcers are the attention and sympathy shown by other people (10).
“Avoidance learning” is another operant mechanism. It implies that certain patterns of behaviour occur be- cause they lead to an avoidance of adverse conse- quenses. “When I show them that I have pain, “bad” things do not happen which otherwise would”. For in- stance, in acute low back pain, rest and avoidance of physical activities serve to reduce pain. In time, the patient learns which type of behaviour reduces (or is assumed to reduce) pain, and thus that specific be- haviour occurs more commonly (9, 10).
Other learning processes (e.g., reinforcement of pas- sive behaviour) influencing the development and main- tenance of pain behaviour have been described by e.g., Linton (9).
Cognitive Factors and Affective Distress
The influence of cognitive factors such as beliefs, in- terpretations, expectancies and fantasies on behaviour and emotional reactions are emphasised in the cogni- tive theories. Emotional reactions and behaviour are as-
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Behaviour in chronic low back pain 383
sumed to be dependent on how the individual inter- prets and evaluates his situation (22). Cognitive ap- praisal is a continous process, a repeated evaluation of the significance of external and internal events. In chronic pain the cognitive approach assumes that cog- nitions influence both the subjective experience of pain, pain-related emotional reactions and pain-related behaviour (4).
An individual’s perceptions of his own capabilities called by Bandura (23) his self-efficacy beliefs seem to be an especially important component of self-evalua- tion. Self-efficacy is a personal belief that one can suc- cessfully perform a required behaviour in a specific sit- uation or that one can successfully cope with an ac- tivity or event. People with a weak belief in their self- efficacy are less likely to persist in actively coping in the presence of difficulties or obstacles (24). People have a tendency to avoid situations that they believe are beyond their capability, and CLBP patients often have a negative self-image including negative expec- tations (16). The negative expectancies of CLBP pa- tients about their ability to perform physical activities such as bending, walking a long distance, climbing stairs etc. lead them avoiding these activities (15).
The self-efficacy beliefs have been found to be relat- ed to pain tolerance, to behaviour and to changes in behaviour (e.g. level of funtioning and response to treat- ment) and they have a potential utility in predicting how individuals wil l respond to or cope with pain (24).
The most successful way to increase a person’s self- efficacy beliefs is probably the experience of success related to actual performance (23, 24). Dolce et al. (24) used exercise quota systems to increase self-efficacy beliefs in patients with chronic pain. Repeated success experienced during systematic exercising was hypo- thesised to provide the patients with information incon- sistent with their previous beliefs of being unable to exercise. A learning of high-efficacy beliefs was sup- posed to occur as a result of this inconsistency be- tween beliefs and actual performance. The results showed that the exercise quota system was effective in increasing activity levels and expectancies of self- efficacy. Many problems, however, are related to changing disability beliefs (16, 24).
Other types of cognitive appraisal influencing pain and disability have also been studied. Overgeneralisa- tion i.e., unjustified generalisation on the basis of a single incident, “It hurt me before, it will always cause me pain” has in some studies been found to be relat- ed to disability (25, 26). Disability or avoidance of phys- ical activities possibly spreads from one area of func- tioning e.g., a set of movements to other areas due to the cognitive process of generalisation. A vicious cir- cle is formed: generalisation increases and maintains disability, and increased disability maintains the in- dividual’s low self-efficacy beliefs.
The relation between psychological distress such as anxiety and depression and chronic pain has been widely studied. Studies on causal relationships gener- ally show that the distress is a consequence of the pain problem, even if the nature of these relations is unclear (27). A study by Sternbach and Timmermans (28) showed that neurotic features associated with chron- ic pain are a consequence of the pain, and successful
intervention leading to reduced pain results in a return to previously normal levels of psychological function- ing. Wood and Main (29) found that the influence of physical and psychological factors on disability changed over time. In a group of acutely ill patients dis- ability was almost totally explained by physical factors, while with increasing chronicity psychological distress in terms of depression, anxiety and preoccupation with bodily symptoms were of increasing importance in de- termining disability.
Depression is said to be common among patients with chronic pain. One assumption is that pain is an equivalent of depression in “pain-prone” persons lack- ing an organic basis of their pain (30). No adequate em- pirical data exists, however, to support the assumption of a “pain prone” personality, and the very basis of the assumption (pain as either “organic” or “psychogen- ic”) is inadequate.
Depression has also been studied using the cogni- tive approach (22). ‘Certain types of cognitive process- es are typical in depressed patients. A depressed per- son’s thinking is characterised by “the cognitive triad”: a negative attitude to himself “ I am worthless”, to the environment ”Nobody cares about me”, and towards the future “It will always be like this”. Lefebvre (25) has shown that depressed patients with low back pain dis- play similar cognitive distortions as do depressed pa- tients in general, and that depression in CLBP patients is a function of both the pain problem and cognitive errors.
Recent studies have given new information about the relations between pain and depression. Turk and Rudy (31, 32) found no direct relations between pain and depression. Depression was determined by the pa- tient’s cognitive appraisal of the influence of pain on his daily life and by the feelings of control over the pain problem. This relation proved to be similar in different patient groups, in men and women, and also after treat- ment. Thus an individual’s apprehension of personal control over the pain or over his life in general and his beliefs in his ability to solve his problems together with his apprehension of the interference of the pain problem on his life (social, work, family) seem to serve as mediating factors between pain and depression.
Relations between Chronic Low Back Pain and Activity
Protectiveness and passivity have recently been regard- ed as causing physical “deconditioning”, thus ag- gravating the problem of pain in CLBP patients (1 1-13). Several factors hypothetically influence this avoidance behaviour. One of them is related to the as- sumption that physical activity causes pain. Recent studies (e.g., 10,14-16) on the relationships between activity and pain, however, have found that activity is not consistently related to the severity of pain. Linton (15) studied the relation between activity and pain in CLBP patients. He compared several measures of ac- tivity with ratings of pain intensity, assuming that pa- tients regulate their activities according to their pain level. The results showed that pain was related to ac- tivity according to interview data and patients’ ratings
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of their ability to participate in activities, but no sig- nificant correlations were found between pain severi- ty and activity as measured by self-monitoring or by ob- servation of behaviour. Schmidt (16) found that the per- sistence of CLBP patients in completing a treadmill test was lower than that of non-CLBP patients, but lack of persistence in the patient group was not related to increased pain levels. So with CLBP patients the avoid- ance of physical activities seems to be based on the assumption that activity increases pain and suffering. Anxiety, fear and erroneous beliefs, rather than a real pain-activity relationship leads to passivity, protective- ness and physical deterioration.
Avoiding an unpleasant stimulus is commonly be- lieved to reduce the fear. Studies on phobias, however, have not supported this assumption. On the contrary, several studies have shown that repeated exposure to feared and avoided activities is an effective way to reduce fear and anxiety (17, 18). In chronic low back pain it has been assumed (14) that the avoidance be- haviour and passivity often seen in patients with chronic pain may be as ineffective in reducing pain as has been the case in the reduction of fear in phobic patients. The passive avoidance behaviour, as opposed to active, adaptive behaviour, leads to physical and psy- chological reinforcement of the invalid status in terms of physical deconditioning, increased sensitivity to stressful stimuli, reduced self-control over pain and lack of reinforcement of “normal” social behaviours (9, 13, 14, 19, 20).
Pain behaviour can also be iatrogenically influenced and aggravated by the health care system (6). The fear of pain is likely to be reinforced by instructions such as ”let pain be your guide” and by the prescription of medication for pain “as needed”. Pain and pain be- haviour are thus reinforced by making passivity and medication (and thus relief) contingent upon the patient’s expression of suffering (4). Some patients seek medical consultation to legitimise their illness, and expectations about compensation may influence their behaviour. Extremely anxious patients, worried about and preoccupied with their symptoms, who are met with reassurance “It is nothing dangerous” or dis- paragement “There is nothing wrong with you” may feel comforted only temporarily, then the persisting symptoms lead to increased anxiety, a search for fur- ther help and a need to “prove that the symptoms are real” (21).
Summary and Implications
It is well known that in CLBP patients the correlation between abnormal physical findings and complaints of pain or other pain behaviours is low (33), and adefinite medical diagnosis is usually impossible (12). In the du- alistic model, where pain is regarded as either “organ- ic ” or “psychogenic”, looking for a single cause of CLBP has led to concepts such as malignering, con- version hysteria, masked depression or compensation neurosis (2, 7). The complex network of various inter- active variables regulating pain behaviour suggests that the dualistic model is oversimplified, and the above concepts are not helpful in understanding the be-
haviour of the individual patient. Behaviours like com- plaints of pain, patient ratings of pain severity and per- formance on an isokinetic lifting test can be influenced by pain sensations caused by an organic lesion but also by many other factors. Mislabelled suffering, learning factors influencing behaviour, maladaptive cognitive processes, motivational factors and affective distress, to name but a few, influence the behaviour of patients. Thus psychological factors are not necessarily equiva- lent to psychopathological disturbances, nor do psy- chological factors represent some mystical process ac- tivated when no somatic explanation of the patient’s symptoms is available. An inferior performance in a lift- ing test in the absence of organic findings (or i f a bet- ter performance could be expected for some other rea- son) does not necessarily indicate malignering or ag- gravation. The setting, the instruction given, the lift- ing technique, the familiarity of the situation, fear, moti- vation influenced by previous experiences and antici- pation of pain, in addition to pain severity and physi- cal capabilities, determine the behaviour of the patient in that specific situation.
The conceptualisation of CLBP as being complex and multidetermined makes a comprehensive ap- proach, including evaluation of medicophysical, be- havioural, cognitive, affective and environmental vari- ables, necessary. The treatment should, accordingly, be individually tailored to correspond to the patient’s situation, needs, and apprehension.
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