In considering whether we can answer the question of whether there is a dose-response relationship in psychologically-based pain management for chronic pain problems, we need to step back a bit and think about what dose-response means. It’s based on a very simple notion of medication, perhaps of analgesia: that a small dose produces a small effect, a medium dose a medium effect, and a large dose … well, maybe a large effect or it could be toxic.
I’ll come back to this issue of the drug analogy at the end. So: what is the dose? The number of hours or the number of weeks? As a clinician, I have often wanted to pack more and more into the limited hours of treatment, or to extend treatment hours or weeks to allow for added content, or more discussion and exploration. I had the opportunity, when involved in a rolling inpatient programme, of comparing four week programmes where we took a week’s break in the middle for Christmas or Easter with those which ran continuously. So the hours were the same, but treatment was spread over more weeks. Our impression, and patients’ comments, suggested that the break in the middle allowed consolidation, experimentation, and then a return to a familiar setting and group to think about how that had gone and to revise plans.
Can the dose, whether in hours or weeks, be disentangled from content? Pain management programmes consist of a mixture of education; goal setting; exercise/stretch/relaxation; problem-solving of the difficulties posed by pain and the effects on mood, with cognitive methods to try to counteract unhelpful thinking patterns; various other components such as involvement of partner or family members, or preparation for return to work, may also be included. The proportion of these varies enormously: some programmes involve several hours’ exercise per day, while others just advise and encourage participants to exercise at home between sessions and devote their time to other aspects. And each of these components can affect any or all of the outcomes: reduced disability, improved mood, improved pain experience, return to work or to other valued activities, or reduced medication intake. Gains in one area boost confidence to tackle others, and the solidarity of other group members and availability of staff expertise provide excellent opportunities to try things differently.
Given all that, I was sceptical about whether a recent study by Waterschoot and colleagues, which combined various studies to produce an overall answer regarding dose response to psychological therapies, would be able to identify any benefits just attributable to dose. But they did – and to weeks of treatment (over 6 weeks), not hours, which varied from just over 6 to nearly 200 hours. But it was impossible to disentangle the effects from content, so we can’t say that regardless of content, the longer the programme in terms of weeks, the bigger the gains.
But the third important factor, beyond dose and content, is the level of difficulty of participants entering the programme. If there were consistent selection, either by clinical staff or by self-selection by patients, of only mildly disabled and distressed people for the briefest programmes, of moderately disabled and distressed people for the medium-length programmes, and the most severely disabled and distressed people for the longest programmes, and all made steady progress at the same rate, they could all end up at roughly the same level of disability and distress at the end. If you didn’t know that patients had been matched to length of programme, it would seem that there was no relationship between length of programme and extent of benefit.
So we need to think more about what changes we think happen during and after pain management, and what implications that has for time. Some physical changes can only be achieved cumulatively, while some cognitive changes might be sudden and substantial – the ‘aha’ moment when understanding shifts. Other cognitive changes – habits of thinking, and ways of seeing the world and oneself, are unlikely to happen rapidly even with an ‘aha’ moment or two. Here it is patients and clinicians, not researchers and statisticians, who will lead the way in establishing trajectories of change in different aspects, and how they relate to one another.
So back for a moment to the drug analogy. Drugs have plenty of effects other than dose-related benefit: adverse effects, and at higher doses, toxicity. It is rare to evaluate adverse effects of treatment, and I know of no investigation of whether too much psychology could be toxic. Nor do we know about delayed effects, or ‘slow-release’. Or about responders and nonresponders, unlikely to be distinguished by genotypes as with some drugs, but what about relative efficiency or inefficiency at processing information presented in particular ways? Again, we don’t know. The whole area is in dire need of some clear thinking about what actually happens in psychologically-based pain management interventions.
Amanda Williams is an academic and clinical psychologist at University College London and at the Pain Management Centre, National Hospital for Neurology & Neurosurgery, active in research and clinical work in pain for over 25 years. Her particular interests are evaluation of psychologically-based treatments, including systematic review, meta-analysis, and guidelines; in expression of pain and its interpretation by clinicians; in assistive technology for people with pain; and in pain from torture. She has written over 120 papers and chapters on aspects of pain and psychology, presents at national and international meetings, and is on editorial boards of several major pain journals.
Waterschoot FP, Dijkstra PU, Hollak N, de Vries HJ, Geertzen JH, & Reneman MF (2014). Dose or content? Effectiveness of pain rehabilitation programs for patients with chronic low back pain: a systematic review. Pain, 155 (1), 179-89 PMID: 24135435
Williams AC (2014). How do we understand dose of rehabilitative treatment? Pain, 155 (1), 8-9 PMID: 24513409