Psychological assessment of the chronic pain patient : an overview

Chair : Amanda C de C Williams, UK.
Cochair : Francois Boureau, France.
Psychological assessment of the chronic pain patient : an overview. Amanda Williams, UK.
Use and misuse of psychiatric and psychological measures. Chris Main, UK
Early assessment of risk of chronicity in acute low back pain. Monika Hasenbring, Ruhr University of Bochum, Germany.

Considerable energy and effort has been devoted to developing psychological measures in pain, but the choice still requires a balance between advantages and disadvantages in terms of coverage, comprehensibility, acceptability to respondents, reliability and validity. There is heavy reliance on self-report, entirely appropriate for subjective experience but inferior, though economical, for measurement of behaviour (such as activities), often the target of intervention. Behavioural measures - for instance, of health care use - are underdeveloped and underused (Kaplan 1990), as are psychophysiological measures and non-questionnaire self-report methods. Many psychological assessments must cover a range of domains of behaviour, cognition and affect, and careful choice is required to achieve adequate coverage without overburdening the respondent. Excellent texts ease this choice : Turk and Melzack (1992) and McDowell and Newell (1996).

Psychological and psychiatric measures have been used in a number of ways in the assessment of chronic pain. Early observations on the apparent similarity between depressed patients and chronic pain patients stimulated investigation of the role of psychiatric disorder in chronic pain. While a proportion of chronic pain patients can be given a diagnosis such as depression, over-restrictive attention specifically using the “mental illness” model has not clarified the psychological impact of pain. The success of CBT as an intervention for chronic pain can certainly be viewed as a treatment for depression, in addressing the hopelessness frequently seen in chronic pain patients, but the primary focus of intervention needs to be psychological processes, rather than psychiatric symptoms. The development of sophisticated psychometric tests such as the MMPI and MMPI-2 (Butcher et al, 1989) have not fulfilled their initial promise, either in clarifying the nature of chronic pain or the possibilities for intervention (Main & Spanswick 1995). More recent developments of specific cognitive measures such as the Coping Strategies Questionnaire (CSQ : Rosenstiel & Keefe, 1983) and the Pain Beliefs and Perceptions Inventory (PBPI : Williams & Thorn, 1989) have been more useful in prediction of outcome of treatment. Psychometric measures do have uses as screening procedures, and as outcome measures, but frequently they are too insensitive to detail the processes of change involved in the rehabilitative process. Most of the best known instruments can be used only as a guide in terms of individual management ; identification of obstacles to recovery requires a new generation of measurement tools validated specifically for use in the context of individualised intervention.

Data on the psychometric qualities of measures are often lacking or apply only to a narrow population. Some of the more widely used measures are conceptually or psychometrically unsuitable for use in pain populations, yet provide comparison data which is valuable. Many of those who use the tests take at face value the claims of reliability and validity, although these qualities refer not to the test but to the conditions under which it was tested. In particular, correlational data is used to substantiate claims of convergent/divergent validity, when what they often show is convergence of item content, far less impressive an achievement than prediction of actual behaviour. Most of the reliability and validity testing is carried out on small and often relatively homogeneous populations, but the measures are likely to be used in heterogeneous populations, sometimes with no overlap (for instance, in age) with the standardisation population. The issue of clinical significance, and clinical meaning of statistically significant differences or changes, is also inadequately addressed by many of those who develop and those who use psychological measures : several alternative methods will be discussed. All these issues are considered further in Williams (1999).

Some measures are securely grounded in theory and/or in clinical practice, where symptom checklists are concerned. Others (stages of change is a good example) bear little relation to identifiable psychological processes, however appealing they are to lay notions of change. This makes their interpretation, and therefore their use, fraught with difficulty. In psychological measures more than in some other areas, demand effects - social pressures on patients to answer in particular ways which accord with cultural values - can distort patients’ responses significantly. A further general consideration is an ethical one : to what use is the measure put, and with what purpose. Selection of patients - and refusal of patients for treatment - is a popular subject and measures are already used with further ones in development. But the sensitivity and specificity of psychological questionnaires is such that many patients will be refused treatment who would have benefited, and the predictive power of the questionnaire, developed post-hoc from a preselected population, is never tested. The question appears to be less a psychological one than one of rationing scarce resources.

One of the simplest ways to obtain a score is to ask a direct question and provide a range of response options. Numerical scales (more evenly distributed than verbal categories) can be used for repeated measurement, including diary and electronic assessment. More complex measures run from a simple checklist - of symptoms, of events, etc. - in which all contribute equally to a single total, to multicomponent weighted questionnaires with or without an overall total. Most assessment measures of cognitive content, process and of affect take the latter form, and may in addition have cutpoints to indicate clinical levels of severity. Validation of cognitive and affective measures, and estimation of cutpoints, is difficult, given that the referent is subjective experience ; recognition of the limitations of validation procedures underpins appropriate use of the data. Very helpful reviews of measurement tools used in pain are recommended : Jensen et al (1991), Keefe et al (1999), and in Turk and Melzack (1992). The distribution of measurement instruments across areas of interest is uneven : there are, for instance, many fewer anxiety measures than depression measures, albeit both are of interest and clinical concern ; and measures of social interaction and support have been neglected, except in quality of life questionnaires. Cognitive content and process is variously addressed by a proliferation of measures, many of which overlap conceptually and in content, and many specific to pain problems. However, few are adequately validated against behaviours of concern.

Recent research in biopsychosocial risk factors for pain chronicity in patients with acute low back or sciatic pain have focused on a variety of biological factors (including parameters of physical examination) ; psychological factors (including chronic stress at work or at home, depression, maladaptive pain-related cognitions and pain coping strategies) ; social factors (including age, sex and social status) ; and occupational factors as possible predictors (Hasenbring 1998). The literature has shown that psychological predictors had the most predictive power : patients who go on to develop chronic pain are more depressed, more chronically stressed at work, and have more catastrophizing or helplessness/hopelessness thoughts as well as using more distracting or suppressing thinking. Furthermore, avoiding activities in order to minimize pain as well as extreme suppressive behavior (the suppression of severe pain in order to endure current activities) are high risk factors for chronicity (Burton et al. 1995, Hasenbring et al. 1994). A series of five prospective studies conducted by our own group revealed maladaptive pain coping patterns as high risk factors for chronic pain, and high levels of depression combined with chronic stress at work as high risk factors for not returning to work. In most studies the amount of variability in outcome criteria could be best described using a combination of biomedical, psychological and social parameters. We therefore propose a multifactorial biopsychosocial risk factor model for the prediction of failed back surgery syndrome. First assumptions regarding interrelations of psychological, biomechanical and neurophysiological factors will be elucidated. In addition, clinical assessments for risk factors will be presented as a tool for identifying patients who need psychosocial intervention in addition to medical therapy.


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