Chronic pain, particularly in the form of chronic lower back pain, has been discussed quite often by our cousin the Musculoskeletal Elf. But, chronic pain can come in many forms, and sometimes it is not completely clear what is causing it at all! This can pose a problem for the evidence base; no neat little boxes within which to explore and test and measure.
Chronic pain is however common – if we take the definition of chronic pain to be pain that occurs on most days for more than 3 months, then it is felt that approximately a staggering 20% of the world population are sufferers. This surely means that there is a wealth of published information from which we can glean how people cope with pain and what assessments and outcomes are to be expected? No?? Oh.
Our antipodean colleagues Burke et al have published a meta-analysis in the British Journal of Clinical Psychology looking at the psychological functioning of people living with chronic pain. This is a useful addition to the literature as it looks at chronic pain from a general perspective; not from a condition perspective or a specific population perspective like a lot of other papers have.
Their main aim was to examine psychological functioning in the presence of chronic pain and provide practical recommendations for assessment and therapy.
The research team looked at four databases (PsychInfo, Scopus, PubMed and The Cochrane Library) and searched for studies that examined the psychological functioning of individuals with chronic pain, published prior to 2014.
The eligibility criteria for study inclusion in the analysis were:
- Patients aged ≥16 years
- Chronic pain: pain on most days for a period of ≥3 months
- Included a healthy control group that was matched to the chronic pain group
- The use of standardised self-report assessment tools in both groups
- Published in English and documented original quantitative research
- Was not a case study (n > 1), and
- Data was provided that allowed calculation of Cohen’s d effect sizes (e.g., mean and SD, t-statistic, or exact p-value).
The study looked at effect size by using Cohen’s d which provides a standardised measure of the difference between the means for the chronic pain and control groups and is widely used in meta-analyses.
Effect sizes were interpreted as:
- d = 0.2 small
- d = 0.5 medium
- d = 0.8 large
- d = 2.0 very large
- d = 4.0 extremely large.
95% confidence intervals were calculated to verify the significant difference from zero and measures of heterogeneity and potential publication bias were also recorded.
The initial search identified 11,211 records and 10,525 were excluded immediately. Of the remaining 686 articles, 110 were suitable for meta-analysis as per the criteria above (1% of initial search).
Cohen’s d and 95% CI
Large effect within chronic pain:
- Somatisation: -1.22 (-1.31 to -1.14)
- Pain anxiety/Concern: -1.15 (-1.28 to -1.01)
- Anxiety: -0.82 (-0.89 to -0.74)
Medium effect within chronic pain:
- Emotional functioning: -0.54 (-0.58 to -0.49)
- Depression: -0.46 (-0.50 to -0.42)
- Anger/hostility: -0.38 (-0.54 to -0.22)
Medium to large effect within control group:
- Self esteem: 0.44 (0.18 to 0.70)
- Self efficacy: 0.96 (0.79 to 1.14)
As may have been predicted due to the broad range of studies looked at, the levels of heterogeneity were high in all measures. The measure for publication bias was felt to be adequate in all categories except Anger/Hostility and Self-esteem.
Compared with controls, the chronic pain group consistently reported experiencing significant and substantial problems in all aspects of psychological functioning.
Overall, the findings confirmed that chronic pain is associated with a range of impairments in psychological functioning. It however has flagged up that physically orientated problems (somatisation and pain anxiety/concern) are greater than depression and general impairments in emotional functioning; contrary to the perception that depression is the most commonly experienced problem.
Don’t get me wrong, patients with chronic pain are more depressed that their healthy peers, but they are comparatively more anxious, both in general and in response to pain.
Self-efficacy (being able to bring about change and demonstrate mastery in their lives) was markedly higher in the control group as was the presence of positive feelings about themselves and their overall self-worth.
It was intended that this meta-analysis assist in determining the clinical utility of specific measures, but this did not prove to need to be the case! With the exception of the measures used to assess anger/hostility; where inconsistent findings suggest that the definition and/or measurement of this area require more careful consideration and examination, the most commonly used measures consistently discriminated between chronic pain and their healthy peers, suggesting that they were all suitable for use in clinical contexts.
Strengths and limitations
The authors identified some limitations of their paper:
- Inconsistent terminology and operationalisation of various psychological domains (e.g., somatisation, anger/hostility) which can make the literature search challenging
- The study size precluded detailed qualitative evaluation of individual studies to exclude sources of potential bias other than publication bias, sample inconsistency and low-quality assessment
- This study focussed on the adult chronic pain population from a general perspective and so results may be less applicable to specific groups, especially those with syndrome-specific sequelae
- The exclusive use of self-report measures may have missed valuable studies
- The nature of the studies cannot infer cause and effect
From a broader perspective it did seem that the eligibility criteria were very strict. This means that a lot of potentially valuable studies might have been excluded when they could have added further weight to the results for example; this meta-analysis looked at 1% of the initial literature search.
It was interesting that the authors commented on the fact that there was a large number of studies which were excluded because they did not report the basic data required to calculate Cohen’s d effect sizes. Standards for data reporting have been under increasing scrutiny over recent years, with a strong push for authors to report more detailed data (including effect sizes) when publishing research. Adoption of these reporting principles in future research would facilitate more comprehensive meta-analyses.
These findings suggest that people with chronic pain are in a debilitating bind.
This may been seen as an understatement; the chronic physical pain that people experience is associated with considerable psychological distress, which is most commonly focussed on physical aspects of the overall experience. Although this physical focus is not surprising in the circumstance, it is likely to heighten their level of attention to, and lower their threshold for, physical symptoms. This may, in turn, further increase the chance that they will notice physical symptoms and interpret them as threatening, thus heightening their distress and discomfort, and perpetuating the cycle. Catch 22?!
Although pain anxiety/concern, somatisation and self-efficacy (particularly pain-related self-efficacy) are common considerations when working with individuals who experience chronic pain, the degree to which they are prioritised in therapy varies greatly. The current meta-analysis suggests that, to help individuals break the pain cycle, evidence-based practice in chronic should prioritise these aspects of psychological function.
Future research to expand the knowledge in this field could include examining specific cohorts (e.g., older people, children, indigenous populations) and other methods of mood assessment (e.g., ICD-10 diagnosis).
Burke ALJ, Mathias JL, Denson LA. (2015). Psychological functioning of people living with chronic pain: A meta-analytic review. The British Journal of Clinical Psychology / the British Psychological Society, 54(3), 345–60. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/25772553