Models

The cognitive behavioural model and the cognitive behaviour therapy (CBT) approach are clearly the dominant current psychological framework and treatment approach to chronic pain. The general cognitive behavioural model is very broad and in some ways very flexible . In fact, all of the other models we present are each more-or-less specific versions of this broader model. The essence of the cognitive behavioural model of chronic pain is rather simple. A key concept is that human emotions and behaviour are determined largely by how one views the world, including common errors and biases . Beyond that, the model proposes that: (a) thoughts, beliefs and behaviour patterns are important in understanding adjustment to chronic pain; (b) thoughts, beliefs, emotions and behaviours interact with each other and with the situations where they occur; and (c) thoughts, beliefs and behaviour patterns can be targeted for change by specific methods of skills – training and learning.

The fear–avoidance model , again, is in many ways a more specific version of the CBT model. It was designed with a focus on catastrophizing and fear and meant to explain not all disabling chronic pain but only some, those cases showing a pattern of phobia-like avoidance. According to this model, two routes are available when one has an acute painful injury. One route includes normal activity re-engagement and recovery. The other includes catastrophising about pain, fear, avoidance, inactivity, possible physical deconditioning, possible depression, persisting pain and becoming stuck in a fear and avoidance cycle.

An alternative or perhaps companion to the fear–avoidance model is what is called the avoidance–endurance model . This model proposed that in addition to the fear–avoidance pathway to disability, there is an opposite pathway, an endurance-related response and subsequent physical overuse. The endurance component in particular seems to include two key psychological components: the suppression of pain-related thoughts and pain persistence behaviour .

Acceptance of pain and acceptance-based approaches to chronic pain are increasingly recognised in chronic pain research and treatment development . There is, however, a wider model behind acceptance, called the psychological flexibility model . Psychological flexibility is defined as the capacity to persist with behaviour or change it in a way that is guided by one’s goals, in touch with what the situation at hand allows and occurring in a context where cognitive-based influences on behaviour interact with direct experiences . It can also be described as behaviour that is open to experience, connected to the present moment and engaged in actions linked to goals and values.

Summary of models

As recent attempts to organise and summarise the range of psychological approaches to chronic pain attest, these are indeed wide and varied . As there is no one unifying model, this must mean that practice is also not unified, and perhaps clinicians’ choices for treatment methods are left to the influences of their preferred model. This non-uniformity and the role of clinician preference may mean that at least some patients are not being matched with the methods and approach that will best meet their needs . Greater uniformity probably requires greater consensus on what are effective treatments and then a more consistent, high level of competency in the delivery of these effective treatments. In addition, matching interventions to patients needs depends on understanding their needs. This in turn leads research to attempt to identify subgroups of patients with specific needs by identifying predictors of poor outcomes, moderators of treatment response and mediating processes during interventions that impact on outcomes.

Summary of models

As recent attempts to organise and summarise the range of psychological approaches to chronic pain attest, these are indeed wide and varied . As there is no one unifying model, this must mean that practice is also not unified, and perhaps clinicians’ choices for treatment methods are left to the influences of their preferred model. This non-uniformity and the role of clinician preference may mean that at least some patients are not being matched with the methods and approach that will best meet their needs . Greater uniformity probably requires greater consensus on what are effective treatments and then a more consistent, high level of competency in the delivery of these effective treatments. In addition, matching interventions to patients needs depends on understanding their needs. This in turn leads research to attempt to identify subgroups of patients with specific needs by identifying predictors of poor outcomes, moderators of treatment response and mediating processes during interventions that impact on outcomes.

Key psychological processes

Psychological factors can relate to patients’ outcome in three ways, all of which have specific implications for clinical decisions: Prognostic indicators (predictors) predict patients’ outcomes independent of interventions; effect modifiers (moderators) are characteristics that influence the direction or strength of patients’ responses to a specific treatment; and treatment mediators are intervening variables that appear to account for the effect of treatment on patients’ outcomes . This section will focus on predictors of poor outcome, which are often conceptualised as obstacles to recovery. Non-physiological predictors of poor outcomes in back pain have often been described as ‘yellow flags’, and early conceptualisation included psychological, social and environmental factors (see also Chapter 6 in this issue) . This review focusses only on psychological processes. The original idea of identifying yellow flags was to reduce the burden of disability, based on the notion that screening for known predictors, and including them in the clinical decision process, should improve care. Sensitivity to these factors could also improve the therapeutic alliance between practitioners and patients and enhance adherence to advice and treatment. In the long term, addressing predictors of poor outcomes at early stages of back pain could improve outcomes and reduce costs, by matching interventions to patients’ needs. The concept of flags has developed over time to include three broad groups: normal, but unhelpful factors; reaction to symptoms; and abnormal symptoms . The last, described as ‘orange flags’, include co-morbid psychiatric disorders, which usually require referral to specialists, while the former can potentially be addressed by general practitioners, physiotherapists and other practitioners commonly consulted for back pain .

Much of the evidence for predictors comes from epidemiological observational studies, in which suspected factors were measured at early stages of back pain (typically in the first 4 weeks) and participants were followed up (typically for 12 months) (e.g., Ref. ). Selection and measurement of outcomes have been varied, but the strongest evidence is based on outcomes that include disability, pain interference and intensity, mood state and absenteeism from work due to back pain. Several systematic reviews have attempted to synthesise the evidence from prospective cohorts to identify predictors . Although there is some contradictory evidence, there is now sufficient evidence to support a link between several specific psychological factors and poor outcomes. These include the following.

Depression

There is robust evidence that low mood, often described as depression, predicts the transition to persistent pain status . A systematic review of prospective cohorts that included psychological predictors found depression to be the strongest predictor of long-term disability . Another systematic review coded the components of nine compound screening tools to identify predictors of three dependent variables: work status, functional status and pain . Depression predicted all three outcomes. This fits well within the growing evidence for the impact of depression on prognosis in other groups with pain . Despite the abundant evidence regarding the impact of depression on outcomes, there is considerably less clarity about interventions that target depression in pain patients . A better understanding of different behaviour patterns within depression in patients with back pain could help develop more targeted interventions.

Fear and avoidance

The fear–avoidance model of Ref. was described in a previous section. This model differentiates between aspects of catastrophic fear, which combine fear with beliefs about threat and damage, and subsequent avoidant behaviours. However, the majority of questionnaires measure beliefs rather than behaviours, and several measures focus on exercise specifically, rather than on daily activities . The concept of avoidance ranges from narrow interpretations of avoidance of specific movement to generalised disengagement with life activities. Possibly because of this lack of clarity, the directional link between avoidance and catastrophic thinking has not been clearly demonstrated, although the two are clearly associated. Other possible factors leading to avoidant behaviour have been proposed, including modelling, misinformation and depression . Further development of a theory about broader conceptualisation of fear and avoidance is needed .

Fearful beliefs about movement, exercise and activity have been linked to poor outcomes in several prospective observational studies (e.g., Ref. ) and to changes in performance in experimental studies (e.g., Ref. ). Patterns of avoidance behaviour also have been shown to correlate with measures of catastrophising and with psychosocial and physical disability in cross-sectional data . Furthermore, among complex patterns of activity, avoidance appears to be the ‘overriding’ feature associated with greater disability in general chronic pain and perhaps more so in back pain . In systematic reviews of prospective cohorts, measures of fear and avoidance have been shown to predict function (e.g., Refs. ) most consistently when the beliefs and the outcomes measured are work-related .

Catastrophic cognitions and anxiety

Catastrophising is defined as a maladaptive cognitive style which focusses on irrational forecasting of future events . In relation to pain, a recent review of concepts and measurements concluded that pain catastrophising is characterised by the tendency to magnify the threat value of the pain stimulus and to feel helpless in the context of pain and by a relative inability to inhibit pain-related thoughts in anticipation of, during or following a painful encounter .

Catastrophising is a key aspect of the fear–avoidance model, but catastrophic thinking has been shown to be related to depression and disability independently of fear, as well as having an influence on outcome via fear . Sieben and colleagues used a time series analysis to test the relationships across time between fear–avoidance beliefs, catastrophising and pain intensity in 44 patients. Their results indicate that peaks on all three measures occur together, but no causal relationships could be ascertained. One problem is distinguishing between overlapping constructs and subtle variations in conceptualisation and measurement of fearful cognitions. Catastrophising is related to anxiety, fear, avoidance and depression. While the overlap between constructs and measurements needs untangling, catastrophic thinking is evidently an important predictor of patient outcomes .

Acceptance

There are more than 45 studies, including several prospective cohorts, showing that acceptance of pain and related constructs, such as values, flexible present-focussed attention, cognitive defusion and committed action, are correlated with reduced distress and disability, with less health-care use, with better general functioning and better work status in groups with chronic pain . Although carried out with heterogeneous groups with different sites of pain, back pain was the largest subgroup in each study. These studies have shown that the predictive role of acceptance of pain is independent of, and larger than, the role of pain intensity.

Pain perceptions and expectations

There is a growing body of evidence suggesting that patients’ perceptions and expectations are related to their recovery from back pain . There is also evidence that such expectations predict response to treatment . Perceptions about back pain having serious consequences, being difficult to control and lasting a long time have been shown to predict more disability in a large cohort of UK primary care consultants . Similar beliefs have been found to predict longer work absence . Patients’ perception of their own ability to cope, and impact on their outcomes, also called pain self-efficacy, has been shown to relate to disability even after controlling for pain intensity and distress . It is also related to physical performance in patients with back pain .

However, the role of patient perceptions and expectations about their back pain is potentially complex. Patients who hold negative expectations for recovery may be less likely to recover, but causality cannot be implied. Patients’ negative expectations may reflect a host of unmeasured obstacles to recovery and the ‘cause’ of poor recovery may reside with these obstacles rather than with the negative expectation per se. Attempting to change expectations in this scenario would not result in improved outcomes. In fact, giving out the message that most people recover quickly and that the patient can expect to do the same could constitute a false reassurance.

Recent years have seen a growing interest not only in patients’ beliefs and expectations about back pain but also in those of health-care providers . Underlying this interest is the assumption that practitioners’ beliefs will affect their clinical decisions and that these beliefs, combined with explicit messages about treatment, work absence, monitoring of pain and the threat of back pain will be transmitted to patients, impacting on their beliefs and behaviours and ultimately on outcomes.

Because of the difficulties in measuring clinical decisions and subsequent patient behaviours, the majority of the evidence stems from self-reports of behaviour by practitioners or reported putative clinical behaviour in response to vignettes of patients. A systematic review of the relationship between practitioners’ beliefs and behaviours concluded that there is moderate evidence that practitioners’ fear–avoidance beliefs are associated with reported sick leave prescription, thus directly influencing patients’ behaviour .

Summary of predictors

There is good evidence for an association between a specific set of psychological predictors, including emotional and cognitive factors, and poorer patient outcomes. However, there is also contradictory evidence about the exact factors involved . Better prediction might depend on more individualised and complex models rather than on univariate approaches.

A large observational study of 20 suspected psychosocial factors found that only a handful of them were unique, independent, prognostic indicators, but all of them were significant predictors of outcomes when considered alone . This suggests overlapping variance between predictors. This, in turn, suggests a need to identify important psychological dimensions that can help to integrate current findings, and this requires better models and theory.

The utility of the evidence on predictors depends on our ability to develop interventions that target and modify the specific prognostic indicators. Arguably, except for one or two trials, this has not been done. This topic is discussed further in Chapter 7 of this issue.

The effectiveness of psychological interventions for back pain

There are now many published randomised control trials (RCTs) of psychological therapies for chronic pain generally, and back pain specifically, and several systematic reviews of these. The most recent review of 35 trials of psychological interventions for chronic pain in general, of which 11 were studies with back pain or back and neck pain, concluded that CBT produces weak effects in improving pain immediately following treatment, small effects on disability with some maintenance 6 months following treatment and small-to-moderate effects in decreasing catastrophising and improving mood immediately following treatment . A systematic review of intensive, multidisciplinary, biopsychosocial rehabilitation for chronic LBP concluded that it improves pain and functioning , but only at more than 100 h of treatment. Another review looked at specific types of psychological treatments including operant, relaxation, biofeedback, cognitive, cognitive–behavioural and combinations of these . The main conclusion was that particular combinations of relaxation and cognitive therapy were superior to waiting list control conditions with regard to short-term pain relief, but the authors caution that only few of the studies (seven of 21) were of sufficiently good methodology. Another review concluded that cognitive–behavioural and multidisciplinary treatments appear to produce short-term pain relief and improvements in functioning for back pain but that there is no evidence that they can do so in the long run .

A more positive result from a systematic review and meta-analysis was produced by Hoffman and colleagues . They extracted 205 effect sizes from 22 identified RCTs of psychological treatment for chronic LBP and found positive effects for CBT on pain-related interference, health-related quality of life and depression. On average, the effects of psychological treatments were small and there was little evidence that psychological treatments were superior to other active treatment comparison conditions. The one exception to this was multidisciplinary treatments including psychological methods, which were superior to other active treatments in improving work-related outcomes, both in the short term and in the long term . Another review identified 35 trials of psychological treatment and 11 trials of interdisciplinary treatment and found good-quality evidence for moderate benefits defined as an effect size of greater than an Standard mean difference (SMD) of 0.5 on pain or disability .