The Process of Pain

Recently, prompted by the Ost meta-analysis, raging debate has occurred in which ACT researchers have justifiably taken offence to the articles’ numerous mistakes and selective inclusion criteria. I, for one, am not worried. Perhaps given this book adventure I am currently living, I’m in a position to grasp the huge amounts of ACT research that has improved people’s lives. However, my frustration at the meta-analysis is that it ignored the plethora of process research that has been conducted. Last week Jason Luoma sent an email to the list tipping his cap to the number of RCT’s in the area of chronic pain. I wanted to add to that sentiment. For me, the major strength of the chronic pain research comes from the amount of process analyses that have been conducted. And the lines of consistency that run through the piece below and the book as a whole tell the same story; there is something about ACT. Below I tip my hat to the ACT pain process research with a segment taken out of the Chronic Pain chapter.

(Note: this is the first rough copy of this chapter; therefore there may be minor grammatical errors and studies missing. If you spot any of these don’t be scared to tell me!)


In addition to the aforementioned outcome studies, much effort has also been made to investigate the roles of important ACT processes in the management of chronic pain. One area that has been thoroughly explored is how higher levels of acceptance may be valuable in helping the patient manage their condition. Studies of this kind tend to involve participants completing a battery of questionnaires in which levels of acceptance are measured against adjustment to pain. These investigations were hugely important in the beginning of this research adventure, as finding that those with higher levels of acceptance experience better outcomes suggested that training acceptance might be a useful way of improving the lives of sufferers.

The first study to investigate this hypothesis (McCracken, 1998) found that greater acceptance of pain was correlated with lower pain intensity, less pain related anxiety and avoidance, less depression, better physical and psychosocial ability, more daily uptime and better work status. Importantly, regression analyses showed that acceptance predicted better adjustment on all measures of patient functioning independent of perceived pain intensity i.e. pain did not have to decrease in order for patient functioning to increase. Since this study a plethora of further efforts have been published lending support to the importance of acceptance in managing chronic pain. McCracken, Spertus, Janeck, Sinclair & Wetzel (1999) found that patients characterized as dysfunctional chronic pain sufferers (chronic pain affects their levels of everyday functioning) reported greater pain related anxiety and less pain acceptance than other types of chronic pain sufferers. McCracken and Eccleston (2003) found that acceptance of pain was strongly associated with improvement on a number of outcomes in comparison to ‘coping’ with pain, although later research by Esteve, Ramirez-Maestre and Lopez-Martinez (2007) suggested that acceptance and coping may be complementary approaches. McCracken (2005) displayed how the influence of social context can affect acceptance of pain, where those who receive solicitous, punishing and distracting responses from people around them tend to record lower levels of acceptance. McCracken and Eccleston (2005) conducted a slightly different study when they measured acceptance of pain on two occasions, roughly 3.9 months apart. Results indicated that acceptance of pain at the beginning of the 3.9 months was significantly related to patient functioning at the end; implying that willingness to have pain and engage in valued activities can lead to healthy functioning. McCracken, Vowles and Gauntlett-Gilbert (2007) conducted a similar study and found that those who indicated a propensity for trying to control their pain had significantly worse functioning than those willing to persist in activities while acknowledging that pain is present. Kratz, Davis and Zautra (2007) found that acceptance moderated the relation between pain and negative affect in women with Osteoarthritis and Fibromyalgia over a 12-week period. In other words, participants with higher levels of acceptance were better able to manage their condition, such that when they experienced sharp increases in pain the expected increases in negative affect did not occur. Although McCracken and Yang (2006) and McCracken and Vowles (2008) found values-based action to be significantly related to patient functioning, and McCracken and Zhao-O’Brien (2010) and McCracken and Velleman (2010) found that being high in psychological flexibility may reduce the impact of chronic pain, arguably the most thorough investigation of the relationship between ACT processes and patient functioning was recently published by Vowles, Sowden and Ashworth (2014), who found through a complex analysis, that each of the ACT processes was related to pain intensity, emotional distress and disability, suggesting that the ACT model is a good fit in the treatment of those with chronic pain.

As well as determining if higher baseline levels of ACT processes improve the likelihood of therapeutic success, much work has also been conducted to determine if changes in ACT processes throughout treatment mediate the improvements seen in primary outcome measures. Vowles, McCracken and Eccleston (2007) were among the first to do this when they asked participants to complete a number of measures prior to treatment, immediately following treatment and at 3-month follow-up. Firstly, although the authors point out that the aim of the investigation was not to study the outcome of treatment, participants recorded significant gains across all outcome measures. However, the articles primary purpose was to investigate the mediating role of acceptance. Results indicated that changes in acceptance of pain accounted for a significant unique variance of the improvements seen in depression, pain related anxiety, physical disability, daily rest and physical performance. In a later study, the same authors found that acceptance mediated the effects of catastrophic thinking (a process that often accompanies chronic pain), on depression, anxiety and physical and psychosocial functioning (Vowles, McCracken & Eccleston, 2008).

Following these studies, in which the acceptance seemed to be an active process contributing to clinical improvement, researchers began to re-analyze past data to determine the role of ACT processes in therapeutic outcome. For example, Vowles and McCracken (2010) conducted a secondary analysis of their previous outcome study (Vowles & McCracken, 2008). In this process analysis they aimed to examine how changes in traditional methods of managing chronic pain compare to psychological flexibility. Results indicated that while changes in psychological flexibility were persistently related to improvements in functioning, traditionally conceived methods were unrelated to improvements. This study is a great example of why a process analysis is important – because it is not enough to know that a treatment package works, we have to know how it works. According to these authors, coping methods thought to be useful with this population may not be related to treatment improvement, but changes in psychological flexibility seem to make an important contribution. In the next couple of years two further mediational analyses of earlier outcome studies were published. Wicksell, Olsson & Hayes (2010) took the data from the Wicksell, Ahlqvist, Bring, Melin and Olsson (2008) whiplash study. Results indicated that psychological flexibility mediated improvements seen in pain disability and life satisfaction. Interestingly, a number of process variables important in CBT did not mediate improvements seen in many of the outcome measures. Wicksell, Olsson and Hayes (2011) then took the data from the Wicksell et al. (2009) pediatric study and found similar results. Namely, that variables consistent with psychological flexibility mediated the effects of ACT based interventions to improve outcome in those with chronic pain.

Recently, two further studies have been published investigating mediation and process. Vowles, Witkiewitz, Sowden and Ashworth (2014) published an open trial in which 117 patients were given a brief ACT based intervention. Results indicated that 46.2% of patients had achieved clinically significant change by 3-month follow-up. Importantly changes in psychological flexibility were found to mediate the improvements found in disability, depression, pain related anxiety, number of medical visits and the number of prescribed analgesics (pain killers). Finally, Vowles, Fink and Cohen (2014) asked participants to complete a weekly diary that assessed pain control and engagement in valued activities over the course of a 4-week ACT intervention for chronic pain. In terms of outcome 47.6% of the patients evidenced reliable disability reduction. In terms of process, the expected pattern of change occurred for 81% of participants, where decreases in pain control and increases in engagement with valued activities reliably reduced disability, and the absence of the pattern was associated with a lack of reliable change.

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