Background: Though we know that psychological interventions for adults with chronic pain are effective, many unanswered questions remain. In particular, we have a poor understanding of how some aspects of treatment, such as treatment ‘dose’, relate to outcome. We also know little about the contribution of specific components included in broad treatment packages, such as CBT.
Objectives: I replicated Williams, Eccleston and Morley’s (2012) Cochrane review of psychological interventions for adults with non-cancer chronic pain (excluding headache)
but extended this in two ways: I investigated the relationship between dose and outcome, and developed a system of categorising treatment content across trials.
Results: 64 randomised controlled trials (N = 7,840 participants) were included. Effect sizes(standardised mean differences) were calculated and used in meta-analysis to explore five outcome domains: pain experience, pain behaviour, emotional functioning, and coping and
cognitive appraisal. My findings converge with previous reviews; psychological interventions were effective, but effect sizes were relatively small. Meta-regression analyses found limited evidence for the moderating role of treatment ‘dose’ on outcome. There was some evidence that the period over which treatment was delivered(i.e. ‘dose in weeks’), may be related to outcome for two out of five outcome domains. In terms of treatment content, trials that appeared to utilise the same broad treatment package (e.g. CBT), often appeared to feature different treatment components. Moreover, treatments described as being distinct (e.g. ACT and CBT) often used similar treatment components.
Conclusions: The relationship between treatment dose and outcome is complex and dependent on the outcome being assessed. Broad labels of treatment types, such as CBT, are vague and do not represent homogenous groups. This suggests that all treatment components are not created equal. I propose single-case design and patient-level data analysis as tools to help further explore treatment components, including treatment dose, and outcome.
