Acceptance and Values-Based Action in Chronic Pain: A Study of Treatment Effectiveness and Process

Transcription

1 Journal of Consulting and Clinical Psychology Copyright 2008 by the American Psychological Association 2008, Vol. 76, No. 3, X/08/$12.00 DOI: / X Acceptance and Values-Based Action in Chronic Pain: A Study of Treatment Effectiveness and Process Kevin E. Vowles and Lance M. McCracken University of Bath and Royal National Hospital for Rheumatic Diseases Developing approaches within cognitive behavioral therapy are increasingly process-oriented and based on a functional and contextual framework that differs from the focus of earlier work. The present study investigated the effectiveness of acceptance and commitment therapy (S. C. Hayes, K. Strosahl, & K. G. Wilson, 1999) in the treatment of chronic pain and also examined 2 processes from this model, acceptance and values-based action. Participants included 171 completers of an interdisciplinary treatment program, 66.7% of whom completed a 3-month follow-up assessment as well. Results indicated significant improvements for pain, depression, pain-related anxiety, disability, medical visits, work status, and physical performance. Effect size statistics were uniformly medium or larger. According to reliable change analyses, 75.4% of patients demonstrated improvement in at least one key domain. Both acceptance of pain and values-based action improved, and increases in these processes were associated with improvements in the primary outcome domains. Keywords: acceptance, values, chronic pain, contextual cognitive-behavioral treatment, acceptance and commitment therapy Chronic pain is a prevalent health concern (Breivik, Collett, Ventafridda, Cohen, & Gallacher, 2006; Verhaak, Kerssens, Dekker, Sorbi, & Bensing, 1998) involving considerable costs in terms of healthcare, lost work productivity, and disability compensation (see Gatchel & Okifuji, 2006, for a review). The experience of chronic pain is also associated with significant disability, emotional distress, and suffering, including pain-related fears, depression, and other psychiatric conditions (Breivik et al., 2006; Dersh, Polatin, & Gatchel, 2002; Von Korff et al., 2005). There is no doubt that chronic pain represents a serious problem for the individual, their family, their community, and our societies in general. Integrative biopsychosocial approaches have become a mainstay treatment for chronic pain, as they seem well-suited to address the complexities involved in these conditions (Turk & Monarch, 2002). Associated cognitive behavioral therapy (CBT) programs have a substantial evidence base supporting their effectiveness. Recent reviews suggest that CBT for chronic pain results in reduced pain, emotional distress, disability, medication use, and healthcare utilization, as well as improved physical, social, and work-related activities (Hoffman, Papas, Chatkoff, & Kerns, 2007; McCracken & Turk, 2002; Morley, Eccleston, & Williams, 1999). Furthermore, these treatments are cost effective, regardless of whether treatment is provided via a single discipline (e.g., clinical psychology) or an interdisciplinary team of providers (Gatchel & Okifuji, 2006; Turk, 2002). These results mirror the degree of Kevin E. Vowles and Lance M. McCracken, Centre for Pain Research, School for Health, University of Bath, Bath, United Kingdom, and Centre for Pain Services, Royal National Hospital for Rheumatic Diseases, NHS Foundation Trust, Bath. Correspondence concerning this article should be addressed to Kevin E. Vowles, Centre for Pain Research, School for Health, University of Bath, Bath BA2 7AY United Kingdom. K.Vowles@Bath.ac.uk success CBT has achieved within medical care settings in general (Compas, Haage, Keefe, Leitenberg, & Williams, 1999; Shadish et al., 1997). Although CBT has documented efficacy, the processes underlying treatment effects remain unclear (Keefe, Rumble, Scipio, Giordano, & Perri, 2004; Morley, 2004). CBT, as an organized system, has traditionally placed significant emphasis on the importance of changes in the content of thoughts and beliefs in the treatment process (e.g., Clark, 1995; DeRubeis, Tang, & Beck, 2001). This is true in chronic pain-related applications as well, where the central roles of catastrophic thinking, cognitive coping styles, and beliefs about pain are frequently emphasized (e.g., Turk & Rudy, 1992; Vlaeyen & Linton, 2000). More recently, there has been increasing interest in refining our account of how thoughts, beliefs, and other psychological experiences have their impact on behavior. Some of this interest has come from studies that have failed to find an independent contribution of cognitive strategies on beneficial treatment outcomes. For example, at least five treatment trials for major depression, including a total of 442 participants, have found that specifically targeting maladaptive or illogical cognitions is not necessary to achieve short- or long-term improvements (Dimidjian et al., 2006; Gortner, Gollan, Jacobson, & Dobson, 1998; Jacobson et al., 1996; Jarrett & Nelson, 1987; Zettle & Hayes, 1987). This pattern of results is also found in treatment trials for anxiety, including generalized anxiety disorder, social phobia, posttraumatic stress disorder, and obsessive-compulsive disorder, where component studies have established that cognitive components are neither superior to behavioral components in achievement of outcomes nor necessary to achieve treatment success (see Longmore & Worrell, 2007, for a review). On the basis of current research, it has been argued that treatment may not need to focus on the logic or semantic meaning of thoughts and beliefs in order to be effective, but rather may focus 397

2 398 VOWLES AND MCCRACKEN on the ways in which thoughts and beliefs have their impact on functioning (Hayes, Strosahl, & Wilson, 1999; Linehan, 1993; Segal, Williams, & Teasdale, 2002; Teasdale, 1997). These theoretical arguments emphasize the importance of the historical and situational context where distressing or discouraging psychological experiences occur as a way to understand their functions or interrelations with patient behavior (Hayes, 2004). Developing treatment approaches that may address these gaps in the empirical literature and theory are referred to as third wave, to note their relationship to earlier operant and cognitive behavioral developments (Hayes, 2004). One of the more actively researched approaches from among these developing therapies is acceptance and commitment therapy (ACT; Hayes et al., 1999; see Hayes, Luoma, Bond, Masuda, & Lillis, 2006, for a review). Key therapeutic processes of this treatment model differ from traditional CBT and include acceptance, or the willingness to experience pain or other distressing events without attempts to control them, and values-based action, or the aligning of actions with desired, personally meaningful purposes rather than with the elimination of unwanted experiences (Hayes et al., 1999, 2006). Treatment methods for establishing these processes involve undermining the ways that language and cognitive processes interact with other nonverbal contingencies in ways that limit healthy functioning. These methods include exposure-based and experiential exercises, metaphorical uses of language, and methods such as mindfulness training. Overall, there is good evidence for the efficacy of ACTbased approaches across a variety of healthcare concerns, including controlled trials of depression (Zettle & Hayes, 1987; Zettle & Rains, 1989), psychosis (Bach & Hayes, 2002; Gaudiano & Herbert, 2006), diabetes (Gregg, Callaghan, Hayes, & Glenn-Lawson, 2007), worksite stress (Bond & Bunce, 2000), and polysubstance abuse (Hayes et al., 2004), as well as uncontrolled trials for a number of other conditions (see Hayes et al., 2006, for a review). It appears that the ACT model leads to effective treatment for pain as well. A small controlled trial by Dahl, Wilson, and Nilsson (2004) showed that 4 hr of ACT substantially reduced sick leave and healthcare use in comparison to usual medical treatment in a group of workers at risk of prolonged work absence due to pain or stress. A case series of 14 adolescents with chronic pain indicated that an ACT-consistent treatment was associated with improvements in school attendance and physical and emotional functioning, as well as reductions in interference due to pain and medication use (Wicksell, Melin, & Olsson, 2007). The findings of a trial of contextual cognitive-behavioral therapy (CCBT), an application of the ACT treatment model to chronic pain (McCracken, 2005), indicated significant improvements in emotional and physical functioning, medication use, and pain-related healthcare visits during treatment in comparison to a no-treatment waiting phase in a sample of 108 adults with chronic pain (McCracken, Vowles, & Eccleston, 2005). Subsequently, it was reported that highly disabled patients requiring inpatient hospitalization for treatment achieved outcomes comparable to a less disabled group not requiring hospitalization (McCracken, MacKichan, & Eccleston, 2007). Three additional sets of analyses support the contention that acceptance is a key process in treatment outcome and behavior change in individuals with chronic pain. The first found that changes in acceptance over the course of treatment were related to changes in depression, pain-related anxiety, physical and psychosocial disability, and physical task persistence (McCracken et al., 2005). These findings were replicated in a second study that used an expanded sample wherein changes in acceptance were found to account for significant and unique variance in changes in outcome measures above and beyond the variance accounted for by changes in pain intensity and frequency of catastrophic thinking (Vowles, McCracken, & Eccleston, 2007). Finally, a third analysis found that a brief ACT-consistent experimental manipulation produced short-term improvements in performance in comparison to a manipulation focusing on control of pain in adults seeking treatment for chronic pain (Vowles, McNeil, et al., 2007). The previous treatment findings with regard to chronic pain suggest that treatment approaches based on the model underlying ACT are effective, associated with the processes identified by the treatment model (i.e., acceptance of pain), and fertile ground for continuing development, particularly in relation to other processes from the treatment model. Therefore, the present analyses had two purposes. First, we sought to perform a detailed examination of treatment outcomes, including tests of statistical significance and analyses of effect size and reliable change (Jacobson, Roberts, Berns, & McGlinchey, 1999) in an entirely new sample of pain sufferers. Second, we sought to extend previous process analysis research by the inclusion of another process, values-based action, in addition to acceptance. We hypothesized that statistically significant improvements in outcomes would be observed at treatment conclusion and at follow-up, in comparison to treatment onset. Furthermore, we expected that the results of the effect size and reliable change analyses would support the clinical relevance of these improvements. Finally, we expected that changes in acceptance and values-based action would be associated with one another and with changes in the outcome variables in support of the treatment model. Participants Method Participants were consecutive referrals accepted for treatment at a tertiary care pain rehabilitation unit in southwest England who began treatment between January 2005 and July This sample was entirely separate from those used in previous analyses involving treatment outcome data (i.e., McCracken, MacKichan, & Eccleston, 2007; McCracken et al., 2005; Vowles, McCracken, & Eccleston, 2007). Selection criteria for treatment included persistent pain of longer than 3 months duration, significant levels of pain-related distress and disability, and agreement with the rehabilitative (as opposed to curative) goals of treatment. In addition, patients who required further medical tests or procedures or who had conditions that could interfere with participation in a groupbased treatment program (i.e., impaired neuropsychological functioning, poorly controlled psychiatric conditions) were excluded. A total of 187 patients began treatment. Of these individuals, 145 (77.5%) were enrolled in a 3-week course of treatment, while the remaining 42 individuals (22.5%) were enrolled in a 4-week course for more complex or disabled cases. Across the entire sample, treatment dropouts were relatively rare; only 16 (8.6%) individuals discontinued treatment voluntarily or were discharged early. The remaining 171 individuals provided data before and after treatment, and 114 (66.7% of treatment completers) also provided data at a 3-month follow-up appointment.

3 ACCEPTANCE AND VALUES-BASED ACTION 399 The sample of individuals beginning treatment averaged 47.3 years of age (SD 11.4) and 12.5 years of education (SD 3.0). The majority were women (64.2%) and White European (98.4%). Most were married or cohabitating (68.4%; divorced, 15.5%; single, 13.4%; widowed, 2.7%). Most were unemployed (76.3%) and receiving some type of disability or wage replacement allowance (76.6%). Median pain duration was 96.0 months (range: 8.0 to months). The most frequently identified pain site was low back (45.9%), followed by shoulder/arms (18.4%), full body (16.8%), legs/pelvic region (11.8%), neck (2.7%), mid-back (2.2%), and other (e.g., head, abdominal; 2.2%). The majority of patients also identified additional pain sites (57.2%). The diagnostic status of most patients (51.2%) was not firmly established or was of a general, nonspecific nature (e.g., chronic pain syndrome, musculoskeletal pain, postsurgical pain ). In the remainder of patients, most identified a diagnosis of fibromyalgia (35.7%), while smaller proportions of patients (all 4.0%) reported other diagnoses (e.g., complex regional pain syndrome, arthritis). Measures Patients completed a standard set of measures at the beginning and end of treatment, as well as at the 3-month follow-up visit. Demographic information was collected as part of a brief background inventory, which asked patients to report on prescribed medications, usual pain intensity on a 0 (none) to 10 (worst imaginable) numeric rating scale, work status, and number of primary care, specialist, and emergency department visits for pain attended in the previous 6 months. The medication information was used to calculate a summary score for number of different medication classes being taken for pain (i.e., weak opioids, strong opioids, nonsteroidal anti-inflammatory drugs, tricyclic antidepressants, muscle relaxants, sedatives, anticonvulsants, selective serotonin reuptake inhibitors, and over-the-counter analgesics). The three types of medical visits were also summed to provide an overall index of healthcare use related to pain. Self-report measures were completed in pen-and-paper format. Research assistants supervised the assessments to aid in completion and to ensure complete and usable data. Performance measures were collected by a qualified physical therapist. Incomplete data were rare; missing responses occurred in less than 5.8% of cases on any single questionnaire. Chronic Pain Acceptance Questionnaire (CPAQ). The CPAQ (McCracken, Vowles, & Eccleston, 2004) is a 20-item measure of pain-related acceptance. It has two subscales. The first, Activity Engagement, measures the degree to which pain and related experiences restrict behaviors (11 items; e.g., I am getting on with the business of living no matter what my level of pain is ; It s a relief to realize that I don t have to change my pain to get on with my life ), and the second, Pain Willingness, measures the extent to which efforts are put in to controlling pain (9 items; e.g., I would gladly sacrifice important things in my life to control this pain better [reverse scored]; I have to struggle to do things when I have pain [reverse scored]). A total score is calculated by summing scores for all items. Respondents were asked to rate the truth of each statement as it applied to them on a0(never true) to6 (always true) scale; higher scores indicate greater acceptance. The total and subscale scores have demonstrated internal consistency, reliability over time, and significant relations with measures of emotional and physical functioning (McCracken & Eccleston, 2005; McCracken et al., 2004, 2005). Chronic Pain Values Inventory (CPVI). The CPVI (Mc- Cracken & Yang, 2006) is designed to assess importance and success in six domains of personal values. Values domains include family, intimate relations, friends, work, health, and growth or learning. Respondents are asked to rate the importance of their values in each domain and success in living according to them on a0(not at all important/successful) to5(extremely important/ successful) scale. Previous analyses of this measure have indicated good internal consistency, concurrent validity, and utility in the prediction of daily functioning in a sample of chronic pain sufferers (McCracken & Yang, 2006). For the purposes of the present study, we used the Values Success subscale score as a measure of values-based action. British Columbia Major Depression Inventory (BCMDI). The BCMDI (Iverson & Remick, 2004) was used as an index of depression. The measure contains 20 items modeled after the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) criteria for major depressive disorder; the first 16 items pertain to symptom severity and, when endorsed, are rated on a1(very mild problem) to5 (very severe problem) scale. The last 4 items pertain to the impact of symptoms on areas of work or school, family, and social life. The symptom score has demonstrated adequate internal consistency, test retest reliability, and good sensitivity and specificity for a diagnosis of major depressive disorder (Iverson & Remick, 2004). Only the symptom summary score was used in this study. Pain Anxiety Symptoms Scale-20 (PASS). The PASS (Mc- Cracken & Dhingra, 2002) is a 20-item measure of pain-related fear and avoidance. Each item is rated on a 0 (never) to5(always) scale. The measure has good internal consistency, a stable factor structure, and strong correlations with the original 40-item PASS (McCracken, Zayfert, & Gross, 1992) and other measures of functioning (McCracken & Dhingra, 2002; Roelofs et al., 2004). Sickness Impact Profile (SIP). The SIP (Bergner, Bobbitt, Carter, & Gilson, 1981) is a 136-item measure of the effects of health on daily functioning. It includes 12 domains, which are combined to form a total score and three composite scores, physical disability, psychosocial disability, and other disability. The SIP has been widely used in rehabilitation and other health care settings (Battié & May, 2001; Bergner et al., 1981). The present analyses used the Physical and Psychosocial Disability subscales, as well as the total score. Physical performance measures. Two direct measures of physical performance were also collected. These included a 2-min walking task, which measured walking speed and yielded a measure of distance traveled, and a sit-to-stand task, which measured strength and activity tolerance and yielded the number of repetitions performed within the space of 60 s using an armless chair and without the use of hands or arms for assistance. Previous analyses have suggested that these tasks have acceptable test retest reliability and relations with self-reports of functioning (Harding et al., 1994; Lee, Simmonds, Novy, & Jones, 2001).

4 400 VOWLES AND MCCRACKEN Treatment Program The treatment program was an adaptation of ACT principles and treatment methods (Hayes et al., 1999), as well as mindfulnessbased methods (e.g., Kabat-Zinn, 1990), to an interdisciplinary rehabilitation treatment setting (McCracken, 2005). Treatment was delivered by a team of psychologists, physical therapists, occupational therapists, nurses, and physicians. Treatment methods explicitly targeted the key processes of the ACT model and were used in the promotion of flexible and effective daily functioning and not to reduce or change pain or other physical or emotional symptoms. These methods included mindfulness training, values clarification, exposure-based techniques, and cognitive defusion exercises to raise awareness of cognitive content and its potential influences on action and to increase contact with direct experience outside of this content. Treatment did not include explicit cognitive restructuring or self-statement analysis exercises, methods for enhancing thoughts of self-efficacy, or training in relaxation and distraction. Details of treatment methods can be found in Hayes et al. (1999), McCracken (2005), and McCracken et al. (2005), and similar methods can be found in Dahl, Wilson, Luciano, and Hayes (2005). As noted, treatment courses were 3 or 4 weeks in duration. Treatment was provided in a group format and consisted of 5 days of treatment per week for 6.5 hr each day. Each day had approximately 2.25 hr of physical conditioning sessions and 1.5 hr of psychological session content, including mindfulness training. The remaining time was devoted to activity skills management and health/medical education. While in treatment, patients lived in normal, unassisted apartment accommodations adjacent to the hospital. Treatment integrity was maintained by manualization, supervision, three clinical team meetings per week, and a onceweekly clinical seminar. Analytic Approach Initially, we performed analyses to assess for potential differences among treatment completers and noncompleters and among those who attended and did not attend the follow-up appointment. Statistical methods included analyses of variance (ANOVAs) and chi-square tests. Second, we evaluated treatment outcomes immediately following treatment and at the follow-up. We used repeated measures ANOVAs to test statistical significance for all variables with the exception of the work status variable, for which we performed a Wilcoxon signed ranks test. Next, we calculated uncontrolled within-subjects effect sizes (Cohen s d) by calculating the difference between Time 2 (posttreatment or follow-up) and Time 1 (pretreatment) mean scores and then dividing the result by the standard deviation of Time 1. Cohen (1988) suggested that effect sizes should be interpreted as small when above 0.2, medium when above 0.5, and large when above 0.8. Fourth, we assessed reliable change between pretreatment and follow-up. Reliable change is one aspect of clinical significance that involves using temporal stability data (i.e., test retest reliability) to test whether scores change to an extent that exceeds change that could be accounted for by measurement error. We calculated reliable change indexes using the formula suggested by Jacobson et al. (1999), which involves calculating a standard error of the difference between assessment points (S diff ) and then using that score to determine confidence intervals for assessing measurement error. The S diff is calculated as follows: SEM 1 SD 1 1 r 12 (standard deviation from Time 1 multiplied by the SEM 2 SD 2 1 r 12 square root of 1 minus the test retest coefficient), (standard deviation from Time 2 multiplied by the S diff SEM 1 2 SEM 2 2 square root of 1 minus the test retest coefficient), square root of the sum of the squared SEMs. We then multiplied the S diff by 1.64 to obtain a confidence interval of.90 (excluding the 5.0% of the distribution in each tail). If the magnitude of change for a certain individual exceeds the confidence interval, that individual can be classified as reliably changed. We performed reliable change analyses for three outcome measures considered to be core domains in chronic pain (e.g., Dworkin et al., 2005), which were depression (BCMDI), disability (SIP), and pain-related anxiety and avoidance (PASS). In addition, test retest information is available for these measures, which is necessary to assess reliable change. 1 Finally, we examined relations among changes in outcomes and changes in acceptance and values-based action. We computed residualized change scores for all measures for two time periods, pre- to posttreatment and pretreatment to follow-up. First, we calculated an overall correlation matrix of these change scores. Next, we conducted multiple regression analyses to determine how changes in acceptance and values-based action, considered together, related to changes in outcome measures, after controlling for relevant background variables. We performed these regression analyses for both time periods. Preliminary Analyses Results In comparison to those who did not complete treatment (n 16), treatment completers (n 171) were younger (M 46.8 years, SD 11.1 vs. M 53.4 years, SD 12.6), F(1, 186) 5.08, p.05, and their pain duration was shorter (M months, SD 89.8 vs. M months, SD 139.1), F(1, 186) 8.90, p.005. No other differences were found on any other measure, including usual pain intensity, number of pain related surgeries, medical visits in the 6 months prior to beginning 1 We did not test the other aspect of clinical significance, which is to determine whether the score of a particular case has moved significantly from a clinical distribution to a normal or recovered distribution, as these calculations require normative data from an appropriate sample for comparison (Jacobson et al., 1999). To our knowledge, there are no data available or appropriate for use as a recovered sample of chronic pain sufferers.

5 ACCEPTANCE AND VALUES-BASED ACTION 401 treatment, gender distribution, marital status, work status, or any of the self-report measures; for ANOVAs, all Fs 2.40, all ps.12; for chi-square analyses, all s 2.4, all ps.49. With regard to the comparisons among those who attended follow-up and those who did not attend, all comparisons were nonsignificant, all Fs 2.79, all ps.10 at posttreatment, and all Fs 1.99, all ps.16 in residualized change from pre- to posttreatment. Outcome at Treatment Conclusion and 3-Month Follow-Up Descriptive information for measures of treatment process and outcome is displayed in Table 1. Observed pretreatment values on these measures appear to be consistent with those observed in other samples of chronic pain patients in that they indicate that patients were complex and, on average, suffering from moderate depressive symptoms, moderate to severe disability and functional impairment, and elevated pain-related fear (e.g., McCracken, Gross, & Eccleston, 2002; Spinhoven et al., 2004; Turner-Stokes et al., 2003; Vowles, Gross, & Sorrell, 2004). Observed physical performance was generally consistent with the studies of Harding et al. (1994) and Lee et al. (2001). Significance Testing Repeated measures ANOVAs indicated significant improvement across all measures of outcome for both time periods, all Fs(1, 170) 50.16, all ps.001 for pre- to posttreatment, all Fs(1, 113) 5.57, all ps.02 for pretreatment to follow-up. If a more stringent alpha level were applied to control for Type I error (i.e.,.05 number of tests performed or ), all analyses would continue to be significant with the exception of reduction in number of medications from pretreatment to follow-up; all other Fs(1, 113) 11.45, all ps.001. Descriptive information is displayed in Table 1. For work status (not shown in Table 1), the results of the Wilcoxon test indicated a significant difference, Z 2.24, p.05. Of those who provided data at the follow-up appointment, 15 had returned to work, 5 had discontinued work, and the work status of the remaining individuals remained unchanged. Descriptively, 29.7% of patients were working at the beginning of treatment and 38.1% were working at follow-up. Effect Size Calculations From pre- to posttreatment, the average effect size was 1.07 (range: ). From pretreatment to follow-up, average effect size was 0.89 (range: ). Specific effect size magnitudes for all measures are displayed in Figure 1. Using Cohen s (1988) suggested interpretive guidelines, we found that changes for all measures were of a large size over the pre- to posttreatment period, with the exception of change in pain intensity, which was medium sized. During the pretreatment to follow-up period, effect sizes remained large for acceptance, depression, pain-related anxiety, walking distance, and sit-to-stand performance, whereas effect sizes were medium for values-based action, pain intensity, physical disability, and psychosocial disability. Finally, the effect size for medical visits was just below medium (d 0.48), in part due to the large baseline standard deviation. Reliable Change Analyses Table 2 shows the results of the reliable change analyses from pretreatment to follow-up at the 90% confidence interval for depression, pain-related anxiety, and disability. Because we were unable to find published test retest data for the physical and psychosocial subscales of the SIP, we used the SIP total score Table 1 Mean Values (Standard Deviations) for Outcome and Process Measures at Assessment Points Measure Pretreatment (N 171) Posttreatment a (N 171) 3-month follow-up a (N 114) Acceptance (total) 50.4 (14.8) 76.4 (17.3) 73.3 (19.3) Activity engagement 30.0 (10.1) 45.2 (10.9) 41.7 (12.0) Pain willingness 20.5 (8.4) 31.2 (10.0) 31.8 (10.5) Values-based action 2.0 (1.0) 3.2 (1.1) 2.7 (1.1) Usual pain intensity 7.0 (1.8) 5.8 (1.9) 5.9 (2.1) Depression 27.4 (12.7) 11.8 (10.7) 15.5 (13.4) Pain-related anxiety 46.3 (18.3) 27.6 (18.5) 27.7 (19.8) Physical disability 0.19 (0.11) 0.10 (0.09) 0.11 (0.10) Psychosocial disability 0.28 (0.16) 0.14 (0.14) 0.17 (0.16) Walking distance (meters/2 min) 95.9 (41.0) (46.7) (50.0) Sit-to-stand task (frequency/1 min) 10.7 (7.1) 19.7 (9.4) 20.8 (11.3) Medication classes 2.6 (1.4) 2.4 (1.5) Medical visits (past 6 months) 5.4 (4.6) 3.2 (3.4) Note. Acceptance was measured with the Chronic Pain Acceptance Questionnaire, values-based action with the Chronic Pain Values Inventory, pain with a 0-10 numerical rating scale, depression with the British Columbia Major Depression Inventory, pain-related anxiety with the Pain Anxiety Symptoms Scale-20, and disability with the Sickness Impact Profile. Medication classes was a summation of classes of medications being taken for pain. Medical visits were calculated by summing pain-related primary care, specialist, and emergency department visits from the previous 6 months. a Pairwise comparisons all significant at a Bonferroni-corrected alpha of.004, with the exception of the medication classes variable.

6 402 VOWLES AND MCCRACKEN Pre-Post Pre-Follow-up Effect Size Acceptance Values-based Action Pain Depression Pain-related Anxiety Physical Disability Psychosocial Disability Walking Distance Sit to Stand Medical Visits Figure 1. Uncontrolled within-subjects effect size statistics (Cohen s d) for outcome measures. Horizontal reference lines in the figure represent small (0.2), medium (0.5), and large (0.8) effect sizes. instead. Rates of reliable improvement were similar across the three measures, averaging 45.0% (range: 41.8% 49.1%). Reliable decline occurred only for the SIP and in only 3.4% of cases. When evaluated on a case-by-case basis, 75.4% (n 86) of patients reliably improved on at least one measure, 61.4% (n 70) reliably improved on at least two, and 14.0% (n 16) reliably improved on all three. On the basis of these results, 1.34 patients would need to be treated to see reliable change on one measure, 1.65 for reliable change on two, and 7.14 for reliable change on all three. Treatment Process Analysis Correlations among residualized change scores for acceptance and values-based action with residualized changes in outcome Table 2 Results From the Reliable Change Analyses From Pretreatment to 3-Month Follow-Up Measure Test-retest % reliable (r) S diff decline % reliable improvement Depression (BCMDI) Pain-related anxiety (PASS) Total disability (SIP) Note. S diff standard error of the difference between pretreatment and 3-month follow-up. Reliable decline and reliable improvement are the percentage of patients completing the follow-up assessment whose scores can be classified as reliably changed according to the formula of Jacobson et al. (1999) at a 90% confidence interval. BCMDI British Columbia Major Depression Inventory; PASS Pain Anxiety Symptoms Scale-20; SIP Sickness Impact Profile.

7 ACCEPTANCE AND VALUES-BASED ACTION 403 variables are shown in Table 3. Across the treatment interval, changes in acceptance were significantly correlated with changes in all measures of outcome, including pain intensity, depression, pain-related anxiety, disability, and both performance measures, such that greater increases in acceptance were associated with greater reductions in distress and disability and greater improvements in performance. Changes in values-based action were only moderately associated with improvements in depression, painrelated anxiety, and sit-to-stand performance. In addition, changes in values-based action and acceptance were significantly related to one another, but this relation was not strong, with overlapping variance of 6.3%, which suggests that these measures were tapping related, but distinct constructs. When residualized changes through follow-up were examined, acceptance remained significantly associated with changes in six of eight outcome measures, again in a direction suggesting that greater increases in acceptance were associated with greater improvements in functioning. Changes in values-based action generally appeared to have stronger relations with changes in outcomes over this interval in comparison to the pre- to posttreatment interval, as relations were larger and significant in relation to changes in five outcome measures. These relations were also in the predicted direction. The relation between changes in the two process measures at follow-up suggested 27.0% overlapping variance. Next, we conducted multiple linear regressions to investigate the unique and combined contributions of changes in acceptance and values-based action in accounting for changes in outcome measures. Variance estimates ( r 2 ) and standardized regression coefficients ( ) for these analyses are displayed in Table 4. We tested demographic variables, including gender, age, education, and pain duration, as predictor variables first, using a statistical entry procedure ( p.05 for entry and p.10 for removal). In general, these variables were not significant predictors of changes in treatment outcome, accounting for significant variance in outcome in only 3 of 15 equations and for 5% variance each time. Following the demographic variables, changes in acceptance and values-based action were simultaneously entered. Over the treatment interval, changes in these measures accounted for significant variance in changes across all measures of outcome (range r , average r 2.15). On each occasion in the preto posttreatment analyses, the magnitude of regression coefficients was significant only for changes in acceptance, which was consistent with the correlation results. Over the treatment to follow-up interval, changes in acceptance and values-based action accounted for significant variance in changes in six of eight outcome measures (range r , average r 2.17). Only variance accounted for in the performance measures failed to achieve significance. Significant regression coefficients were found for either values-based action or acceptance in each of the same six equations. Regression coefficients were significant for acceptance on two occasions, for pain-related anxiety and medical visits, and for values-based action on four occasions, for pain, depression, and both disability measures. Discussion The present analyses involved an in-depth assessment of the effectiveness of a contextual, ACT-consistent, interdisciplinary group treatment for chronic pain. In addition, two processes from the treatment model, acceptance and values-based action, were examined for their contributions in relation to changes in outcomes. In sum, our hypotheses were supported, and the results provide additional evidence for the treatment model. Immediately following treatment and at follow-up, our sample of complex pain sufferers achieved significant reductions in depression, pain-related anxiety, disability, and healthcare use and significant improvements in physical performance measures. Average improvement on outcome measures at posttreatment was 47.3% (range: 17.1% for pain to 84.1% for sit-to-stand performance) and at follow-up was 40.6% (range: 7.7% for medication use to 94.4% for sit-to-stand performance). Effect sizes were uniformly of a medium size or larger, with the sole exception of number of medical visits, which was of a small size. Furthermore, the percentage of individuals working improved by just under 10% from pretreatment to follow-up. These outcome findings mirror results from other ACT-focused interventions for chronic pain (i.e., Dahl et al., 2004; McCracken et al., 2005; McCracken, MacKichan, & Eccleston, 2007; Vowles, McCracken, & Eccleston, 2007; Wicksell et al., 2007) and add to the overall pool of data supporting the effectiveness of this treatment approach (Hayes et al., 2006). Table 3 Correlations Among Residualized Change Scores of Acceptance and Values-Based Action With Treatment Outcome Measures Pre- to posttreatment Pretreatment to follow-up Measure Acceptance Values-based action Acceptance Values-based action Values-based action.25 **.52 *** Usual pain intensity.23 ** **.30 ** Depression.39 ***.19 *.30 **.41 *** Pain-related anxiety.66 ***.17 *.56 ***.44 *** Physical disability.43 *** **.39 *** Psychosocial disability.36 *** ***.40 *** Walking distance.21 ** Sit-to-stand task.24 **.17 * Medical visits.32 ***.15 * p.05. ** p.01. *** p.001.

8 404 VOWLES AND MCCRACKEN Table 4 Regression Results Using Residualized Changes in Acceptance, Values-Based Action, and Treatment Outcomes From Pre- to Posttreatment and Pretreatment to Follow-Up Step and predictor Pre- to posttreatment r 2 Pain intensity Pretreatment to follow-up (final) r 2 (final) Step 1.04 *.10 ** Acceptance.21 *.13 Values-based action * Depression Step 1.05 * Pain duration.23 ** Step 2.19 ***.17 *** Acceptance.36 ***.15 Values-based action ** Pain-related anxiety Step 1.41 ***.33 *** Acceptance.63 **.46 *** Values-based action Physical disability Step 1.04 * Education.21 ** Step 2.18 ***.14 *** Acceptance.41 ***.13 Values-based action ** Psychosocial disability Step 1.04 * Education.22 ** Step 2.16 **.17 ** Acceptance.30 ***.21 Values-based action * Walking distance Step 1.04 *.02 Acceptance.20 *.06 Values-based action Sit-to-stand task Step 1.06 *.02 Acceptance.21 *.03 Values-based action Medical visits Step 1.10 ** Acceptance.32 ** Values-based action.01 * p.05. ** p.01. *** p.001. Two sets of outcome findings, in particular, are noteworthy. First, the reliable change analyses suggested that three fourths of patients treated demonstrated reliable improvement in depression, pain-related anxiety, or overall disability at follow-up and almost two thirds of these patients demonstrated reliable improvement in two of these domains. Given the longstanding nature of the pain experienced by these patients, the lack of benefit from previous treatments, and the stringent statistical criteria that must be met to achieve reliable change (Jacobson et al., 1999), the fact that the majority achieved reliable change in two of three measures of functioning is important and reinforces claims regarding the efficacy of the treatment provided, as well as the efficacy of the broadly behavioral and cognitive treatments for chronic pain (Gatchel & Okifuji, 2006; Hoffman et al., 2007). Second, the reduction in medical visits and unemployment all have real-world value in that these reductions directly translate into cost savings, increasingly important given the numerous strains on healthcare financing and disability compensation systems (Gatchel & Okifuji, 2006; Turk, 2002). Both acceptance and values-based action improved significantly over the time periods analyzed. In relation to pretreatment scores, acceptance improved by 51.6% and 45.4% at posttreatment and follow-up, respectively, whereas values-based action improved by 60.0% and 35.0% at posttreatment and follow-up, respectively. Effect sizes for both measures were uniformly above 0.7. In particular, the effect sizes for acceptance are notable, as they were the largest across all assessed variables. On average, acceptance scores improved by over 1.5 SDs relative to pretreatment. One explicit goal of treatment was to increase acceptance; the large shifts in this measure demonstrate that treatment effectively achieved that goal. The effect size for values-based action was large immediately following treatment and medium at follow-up, where there may be additional practical and psychological factors influencing the success of values-based action. As far as we know, this is the first and only study to examine values-related processes in treatment for chronic pain. In the future, it will be interesting to further investigate patterns of change in values-based action in treatment and how these relate to patient functioning over the longer term. In the analyses of treatment process, changes in acceptance and values-based action were related to changes in outcomes in expected directions, such that increases in these processes were associated with improvements in functioning. Acceptance and values-based action accounted for a fair to moderate proportion of variance in improvements following treatment, averaging 15.4% when using the pre- to posttreatment interval and 16.8% using the pretreatment to follow-up interval. The pattern of results over these two time periods, however, was different. Changes in acceptance appeared to dominate in the process of treatment over the pre- to posttreatment interval, while changes in values-based action appeared to dominate over the pretreatment to follow-up interval. Changes in acceptance at follow-up remained important for painrelated fear and medical visits. This pattern of findings from the regression analyses suggests an interesting and theoretically plausible interpretation. In short, an early focus in treatment on acceptance may facilitate the role of later values-based action. For example, one aspect of acceptance involves a redirection of the struggle to control pain and all the related aversive experiences that go along with it (e.g., emotions and other symptoms). As long as behavioral efforts are directed at avoiding aversive and unpleasant experiences, actions may be limited to those that do not involve discomfort, which is not always a practical option for those with chronic pain. It may be sensible to

9 ACCEPTANCE AND VALUES-BASED ACTION 405 address the problem relating to avoidance of discomfort in the earlier stages of treatment, as this may aid in the development of increased flexibility in behavior and create more opportunities for values-based action to occur. This explanation is consistent with that of Hayes et al. (2006), who noted that fostering acceptance in treatment is not itself an end but that it is fostered as a means of increasing values-based action. A specific strength of the ACT model is its identification of six interrelated therapeutic processes: acceptance, values identification/values-based action, contact with the present moment (e.g., an aspect of mindfulness), cognitive defusion, self as context, and committed action (Hayes et al., 2006). The explicit focus on these particular processes within ACT is what distinguishes it from other approaches within the broadly cognitive and behavioral therapies. Previous research in chronic pain has focused on four of these processes: acceptance (see McCracken & Vowles, 2006, for a review), values (McCracken & Yang, 2006), mindfulness (McCracken, Gauntlett-Gilbert, & Vowles, 2007; Sephton et al., 2007), and cognitive defusion (Vowles, McCracken, & Eccleston, in press). In each study, as in the present one, the model has been supported. As behavior is influenced less by the struggle to think correctly or feel good, more in contact with direct experience, less entangled with verbally constructed versions of reality, and more successfully guided by values, then improved social, emotional, and physical functioning is observed. There is a need to continue to study the ACT model, as a whole, with each of its constituent parts considered together. To further clarify, acceptance is not a matter of how one is thinking or feeling per se. It is in the quality of action in contact with thinking or feeling, particularly in relation to uncomfortable or negatively evaluated experiences (Hayes et al., 1999; Mc- Cracken, 2005). This quality includes a willingness to have, and not struggle with, these experiences. Likewise, engaging in valuesbased action is not regarded as contingent on thinking logically or positively, nor on feeling good, confident, or relaxed. Valuesbased action includes qualities that give behavior patterns a positive and meaningful direction, even when, or especially when, other concurrent experiences might urge a different action. In each case, the focus is not particularly on the content of thoughts or beliefs, but on the interaction of thoughts and beliefs, and verbally based influences in general, with nonverbally based influences, as well as the contexts within which these interactions occur. No randomization to a control condition was included in the present treatment trial, which can appear as a significant limitation. However, this limitation is mitigated in several ways. First, there are previous trials of ACT-based treatment for pain that included control conditions and each demonstrated positive results (Dahl et al., 2004; McCracken et al., 2005; McCracken, MacKichan, & Eccleston, 2007). Second, the patients treated in the present study had complex longstanding problems, and they showed moderate to large improvements at posttreatment and 3 months later, results that would be highly unlikely to occur except from some specific process of treatment. Third, changes were demonstrated across multiple domains and on self-report and objective measures of functioning, again, results not likely to occur in the absence of an actual treatment effect. Finally, the treatment examined here occurred in a real life clinical situation with a group of relatively unselected patients suffering from substantial distress and disability and with a history of many ineffectual treatments. Taken together, these circumstances make it highly unlikely that the patients treated in this study would have made similar improvements solely with the passage of time or due to demand characteristics alone, to name just a couple potential threats to internal validity. There are at least three other limitations that deserve consideration. First, the current results were obtained under highly specific conditions. Treatment was interdisciplinary, intensive, residential, provided in a tertiary care setting, and followed a clearly specified theoretical model. It is possible that the present findings may not generalize to chronic pain patients treated under different circumstances. Second, although treatment gains persisted at the 3-month follow-up appointment, the longer term effectiveness is unclear. Finally, the amount of change in analgesic medication use was small and nonsignificant when a Bonferroni-corrected alpha was used. Although analgesic use is a complex behavior and not always maladaptive, it is intriguing that use continued relatively unchanged even after substantial improvements occurred in the other measures. It may be that our method of quantifying medication use was not sensitive enough to detect changes or that our treatment methods were not directly focused on medication use with enough intensity to generate a significant impact. The process of change in medication use will require further study to determine how to alter these patterns of behavior and if continued medication use impacts on longer term functioning after treatment. In summary, an intensive, group-based program of treatment for chronic pain that is based on the model underlying ACT was associated with significant and clinically reliable change across a number of areas of functioning. Shifts in two hypothesized treatment processes, acceptance and values-based action, were related to shifts in outcomes. These findings provide support for the ACT model of treatment (Hayes et al., 1999) and a specific application of it to chronic pain, CCBT (McCracken, 2005). Future investigations attempting to replicate and extend these results may benefit from the addition of comparison conditions, the inclusion of other process variables from within the same treatment model, longer term follow-up assessments, and perhaps tests of generalizability to other settings, formats, and patient groups. References American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Bach, P. B., & Hayes, S. C. 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