Editor’s note: The following is a summary of the Professor Tess Cramond Named Lecture from the Australian Pain Society 39th Annual Scientific Meeting, which took place from April 7 to 10, 2019, on the Gold Coast, Queensland, Australia. Cramond began her career as an anesthetist in the early 1950s and made significant international contributions to the improvement of anesthesia, resuscitation, and pain medicine. Since 2007, the Tess Cramond Lecture has been presented by an Australian early-career researcher. The 2019 Tess Cramond Lecture was delivered by Melissa Day, University of Queensland.
There is a significant psychological component to chronic pain, and over the last several decades, a number of different psychological treatments have been offered to people with chronic pain. However, many questions remain about the mechanisms underlying many of these therapies—how, exactly, do they work?
In the Tess Cramond Lecture at the 2019 Annual Scientific Meeting of the Australian Pain Society, Melissa Day, University of Queensland, shared recent research findings in this area. She described results from human studies that investigated how treatments like mindfulness and cognitive behavioral therapy (CBT) work, offering the take-home message that enhancing the understanding of treatment mechanisms will help in the development of better and more personalized psychological treatments for chronic pain.
Different treatments, the same results?
The list of effective, evidence-based psychological treatments for chronic pain spans from behavioral therapy to CBT, and in more recent years, to mindfulness- and acceptance-based interventions. These approaches have been shown to be as effective as pharmacological and surgical treatments with respect to both outcomes and cost.
However, Day explained that when these and many other psychological treatments are compared, the “dodo bird verdict” (or effect) becomes apparent. The dodo bird effect has long been debated in the psychotherapy field and refers to the claim that all the different psychotherapies have similar effectiveness. It is named after the Dodo character featured in Lewis Carroll’s Alice’s Adventures in Wonderland, who proclaims at the conclusion of the Caucus Race, “Everybody has won and all must have prizes.”
One of the problems with the dodo bird effect is that many studies compare group averages of treatments. But, “We know that there is a large degree of individual variability in the treatment response,” Day said. “This means that two or more people that we actually treat in the clinic may not have the same response to CBT as each other.” That one individual could have a large beneficial response to CBT, whereas another could have next to no response or even get worse highlights the continued need to streamline and optimize treatment options for each person; some patients are at risk of being overlooked when only group averages are considered.
Shifting the focus to mechanisms
Over the last decade there has been a shift in the line of questioning about psychological treatments for chronic pain. Less focus is placed on whether they are effective, with greater emphasis on how they work.
Day went on to introduce mechanism theory in the field of psychology—the idea that psychological treatments have unique and discrete theoretical bases from which their mechanisms of action are derived. There are numerous models within this overarching theory.
The Specific Mechanisms Model says that treatments work the way we think they do by targeting unique processes or constructs. One example is that CBT targets pain catastrophizing, which is a negative pattern of emotional and cognitive reactions to pain. Similarly, mindfulness-based interventions aim to change the way one thinks about the present moment by viewing it with openness and without judgment. According to the Specific Mechanisms Model, changes in the mechanism targeted by a treatment leads to improvements in pain outcomes. In contrast, the Shared Mechanisms Model proposes that if two treatments target the same underlying mechanisms, then these treatments will have similar effectiveness.
To put these models to the test, Day highlighted results from a 2016 secondary analysis of randomized controlled trial data by Judith Turner, University of Washington, Seattle, US, and colleagues (Turner et al., 2016). The researchers recruited 342 adults with chronic low back pain and who were randomly allocated to receive one of three treatments: mindfulness-based stress reduction (MBSR), CBT, or usual care. They then set out to examine the effects of these three treatments on mindful non-reactivity (allowing thoughts and feelings to arise and pass without judgment) and pain catastrophizing.
The secondary analysis showed that MBSR—again, presumed to work on mindfulness, not catastrophizing—resulted in a larger reduction in catastrophizing compared to CBT. This is not what would be expected according to the Specific Mechanisms Model. The analysis also showed that while both MBSR and CBT were beneficial on mindful non-reactivity, neither treatment was more effective than the other on that measure.
“This research showed very little support for the Specific Mechanisms Model, as we would expect to see a greater effect of CBT on pain catastrophizing [compared to MBSR], and a greater effect of MBSR on mindful non-reactivity [compared to CBT],” Day said. “What we would wonder from that is whether CBT and MBSR—two theoretically unique treatments—work via shared mechanisms.”
One mechanism to rule them all?
As the above study did not specifically investigate the mechanisms underlying the effects of the treatments, Day and her colleagues undertook a pilot study earlier this year to do just that (Day et al., 2019). This investigation compared the effects of mindfulness meditation, cognitive therapy, and mindfulness-based cognitive therapy (which uses cognitive therapy in combination with mindfulness meditative practices) in a cohort of 69 adults with chronic low back pain. The primary outcome of the pilot study was pain interference, which is the extent to which pain interferes with daily activities. The mechanisms examined included pain catastrophizing and mindful non-reactivity.
As with the work from Turner and colleagues, Day and her fellow researchers also undertook a secondary analysis of the data from their initial study, this time to determine if the underlying mechanisms of the three treatments were unique. All three treatments resulted in similar reductions in pain catastrophizing and mindful non-reactivity, again showing no support for the Specific Mechanisms Model. These results led Day and her team to ask how the changes in pain catastrophizing and mindful non-reactivity related to the changes in pain interference. It turned out that reducing pain catastrophizing played a more important role with respect to improving pain interference, compared to improving mindful non-reactivity.
“This raises the question of whether the reduction in pain catastrophizing is a meta-mechanism,” said Day. If so, this would mean that pain catastrophizing is a shared mechanism that can be targeted as part of many, if not all, psychological treatments. “Is reducing pain catastrophizing the most important thing if we want an effective psychological treatment, regardless of if we do this via CBT or via mindfulness-based interventions?” Day asked. This would provide further support for the Shared Mechanisms Model.
Two previous studies support the idea of pain catastrophizing as a meta-mechanism. One of those studies compared the effects of CBT versus pain education, and another compared the effects of CBT versus physical therapy (Thorn et al., 2011; Smeets et al., 2006). Both studies found that reductions in pain catastrophizing predicted improved pain outcomes.
“The tempting conclusion, based on the evidence, is that all have run the race via the same pathway, and everybody has won and all must have prizes,” Day said. According to this somewhat more elaborate dodo bird effect, different psychological treatments elicit their effect through a shared mechanism—a reduction in pain catastrophizing.
“However, the limitation with drawing this conclusion is that we have the same problem in mechanism research that we do in efficacy research—a lumping problem,” Day said. “Just as we are looking at average effects to determine the efficacy [of a treatment], we are looking at group average changes in processes to come to our conclusions about the underlying mechanisms. It’s quite possible that the mechanisms vary as a function of whether an individual responds to the treatment or is a non-responder to the treatment.”
Further research is necessary to address this, starting with a more nuanced investigation of the underlying mechanism pathways between treatment responders and non-responders. Day has confidence that the pain psychology research community will make good progress toward this end. As for now, whether the dodo bird verdict remains in effect, or will go extinct like the famous bird itself, remains to be seen….
This research summary was originally published on Pain Research Forum and is reproduced with permission.