Upload
trantu
View
214
Download
1
Embed Size (px)
Citation preview
Published in:
International Journal of Behavioral Medicine (2016) DOI: 10.1007/s12529-016-9539-x
Title: A validation and generality study of the Committed Action Questionnaire in a Swedish
sample with chronic pain
Sophia Åkerblom1,2; Sean Perrin2; Marcelo Rivano Fischer1,4; Lance M McCracken3
1Department of Pain Rehabilitation, Skåne University Hospital, Lund, Sweden 2Department of Psychology, Lund University, Lund, Sweden3King's College London, Psychology Department, Health Psychology Section, UK4Department of Health Sciences, Lund University, Lund, Sweden
Contact information for the corresponding authorSophia ÅkerblomDepartment of PsychologyLund UniversityBox 213, 221 00 Lund, SwedenEmail: [email protected]: +46(0)46-172-610Mobile: +46-707-790-415
Abstract
Purpose: Psychological flexibility is the theoretical model that underpins Acceptance
Commitment Therapy (ACT). There is a growing body of evidence indicating that ACT is an
effective treatment for chronic pain but one component of the model, committed action, has
not been sufficiently researched. The purpose of this study is to validate Swedish-language
versions of the full length CAQ (CAQ-18) and the shortened CAQ (CAQ-8), to examine the
generality of previous results related to committed action and to further demonstrate the
relevance of this construct to the functioning of patients with chronic pain.
Methods: The study includes preliminary analyses of the reliability and validity of the CAQ.
Participants were 462 consecutive referrals to the Pain Rehabilitation Unit at Skåne
University Hospital.
Results: The Swedish-language version of the CAQ (CAQ-18 and CAQ-8) demonstrated
high levels of internal consistency and satisfactory relationships with various indices of
patient functioning and theoretically related concepts. Confirmatory factor analyses showed
that the factor structure in the current sample matched the two-factor model found in the
original validation studies. Hierarchical regression analyses identified committed action as a
significant contributor to explained variance in patient functioning.
Conclusions: The development, translation and further validation of the CAQ is an important
step forward in evaluating the utility of the psychological flexibility model to the treatment of
chronic pain. The CAQ can both assist researchers interested in mediators of chronic pain
treatment and further enable research on change processes within the psychological flexibility
model.
1
Keywords
Committed action questionnaire, chronic pain, psychological flexibility, psychometric
properties, assessment
Introduction
Acceptance and Commitment Therapy (ACT) is establishing itself as an effective treatment
approach for chronic pain (1). The core therapeutic focus of ACT is on psychological
flexibility (2). The psychological flexibility model includes acting in accordance with
personal goals and values, in the presence of potentially interfering thoughts and feelings,
without being unnecessarily limited by these thoughts and feelings, and with a greater
appreciation of what their current situation or context allows (3). Questionnaires have been
developed or adopted to measure several components within the model, such as acceptance
(4), present-focused awareness (5), cognitive defusion (6), values (7), and numerous studies
have shown that these components underlie improvement in treatment of chronic pain (8-13).
Committed action is a component of psychological flexibility that has not been investigated to
a large extent (14). Committed action can be defined as flexible persistent behaviour patterns
directed towards values and goals. They are persistent in the sense that specific actions can
include failure and discomfort and still continue. They are flexible in that, if they are reliably
experienced as unsuccessful, they can change (14). It has been argued that a focus on
committed action may create an advance in understanding around “activity
pacing”,“overactivity”, “underactivity”, and other activity-related concepts commonly applied
in cognitive behavioural therapy for chronic pain (14, 15).
In an attempt to more fully measure psychological flexibility McCracken (2013) developed
the first measure of committed action, the Committed Action Questionnaire (CAQ). (14) A
2
shortened version CAQ-8 has also been developed. (15). Both the original and the shortened
version revealed satisfactory reliability and validity
The purpose of this study is to validate Swedish-language versions of the full length CAQ
(CAQ-18) and the shortened CAQ (CAQ-8), to examine the generality of previous results
related to committed action and to further demonstrate the relevance of this construct to the
functioning of patients with chronic pain. The study includes preliminary analyses of the
reliability and validity of both measures. Internal consistency of the CAQ and model fit of
the proposed factor structure will be assessed. The criterion and construct validity of the CAQ
will be explored by assessing its relationship with patient functioning and the theoretically
related concepts pain acceptance and psychological flexibility. Also, the unique contribution
of the CAQ within the overall psychological flexibility model is investigated. The incremental
validity is explored by investigating whether the CAQ is able to account for variance in
patient functioning over and above the effect of pain acceptance and kinesiophobia. The
validity analyses in this study are intended to expand the results from the original validation
studies since comparisons include kinesiophobia, an additional construct that is also highly
relevant for in chronic pain. (16) As there are only three previous studies of the CAQ, and two
of these were conducted in the same treatment center in the UK, the current study represents
an important test of the generality of these previous results. (14, 15, 17). Results are expected
to support the usefulness of both versions of the measure for further research within the field
of chronic pain.
Three hypotheses were tested in the present study. Firstly, significant relationships were
expected between the CAQ and the construct as well as the criterion variables, consistent with
a potential role of committed action as a contributor to healthy functioning. Based on previous
research and the psychological flexibility model, at least moderate positive correlations were
expected between the CAQ and pain acceptance and psychological flexibility. Moreover,
3
moderate negative correlations were expected between the CAQ and depression and anxiety.
Moderate positive correlations were expected with vitality, social functioning, general health
and mental health and a small positive correlation with physical functioning. (3, 14, 18)
Secondly, again in line with the psychological flexibility model involving several related but
distinct constructs that contribute to psychological flexibility, the CAQ was expected to make
a significant contribution to explaining the variance in psychological flexibility together with
pain acceptance. Thirdly, the CAQ was expected to make a significant contribution to
explaining the variance in patient functioning after accounting for the contribution of pain
acceptance and kinesiophobia. (3, 18)
Methods
Participants
Participants were 462 consecutive referrals scheduled for assessment at the Pain
Rehabilitation Unit at Skåne University Hospital between August 2013 and January 2015.
The unit is a government supported, regional specialist center where patients are admitted if
they have symptoms of chronic pain that impacts significantly on everyday life. Patients
admitted to the clinic and who meet eligibility requirements are offered intensive, multi-
disciplinary, day treatment based on a cognitive behavioral model. All participants gave
written informed consent prior to their data being used in the study. The study was approved
by the Regional Ethical Review Board in Lund, Sweden (2013/381).
The sample consisted of 333 women (72.1 %) and 129 men aged between 18 and 67 years (M
= 41.0, SD = 11.2). About half (51.9%) were currently in work or studying at least on a part-
time basis. The majority (74.9%) were born in Sweden or another Nordic country. Slightly
more than half (53.9 %) had upper secondary school as their highest education level with a
4
further 26.4 % having studied at university level. These demographics are similar to those
reported by tertiary pain clinics in the 2015 report from the Swedish Quality Registry for Pain
Rehabilitation (i.e., 76% of patients are women and 25% have studied at university level)
(19). The most common diagnoses were fibromyalgia (25.9 %), cervicocranial syndrome
(11.7 %), cervicobrachial syndrome (8.3 %) and myalgia (6.2 %). The average duration of
pain was 7.6 years (SD =7.6) with the number of pain locations varying between 1 and 36 (M
= 14.9, SD = 8.9). Average pain intensity over the past week (rated on a 0-10 scale) was 7.5
(SD = 1.5).
Translation of the CAQ
In translating and back-translating the measure, we followed internationally recommended
guidelines (20). Briefly, the CAQ was first translated from English to Swedish by a Swedish
clinical psychologist fluent in English and with specific knowledge of the research area. The
questionnaire was then back-translated by a Swedish psychologist fluent in English and with
experience in working with instrument translation and validation. Thereafter the translated
and back-translated versions were evaluated by an ‘expert’ group comprised of clinical
psychologists working in the field of pain rehabilitation who were fluent in Swedish and
English, as well as the author of the English language original. The questionnaire was updated
and changed according to suggestions of the expert group. In the penultimate step, the ‘final’
Swedish language version of the CAQ was administered to 10 current patients at the pain
clinic and they were asked to give feedback on the clarity of instructions and the vocabulary
used. Final adjustments were made and the updated version was then approved by the expert
group and administered to new referrals as part of a larger package of standardized
questionnaires.
5
Measures
Self-report data were collected by mailing measures to the homes of newly referred patients to
be completed before their first full clinical assessment (diagnosis, functioning, and suitability
for treatment) at the clinic. In addition to the measures listed below, patients reported their
age, gender, education, country of birth, marital status, work status, pain sites, and pain
duration.
Committed Action Questionnaire (CAQ-18): The CAQ measures goal-directed, flexible
persistence and has 18 items each rated on a seven-point scale (0 = never true to 6 = always
true) (14). The CAQ has two components, derived from factor analysis and based on how the
items are phrased: Factor 1consists of nine positively phrased items (e.g., “When I fail in
reaching a goal, I can change how I approach it”) and Factor 2 of nine negatively phrased
items (e.g., “When I fail to achieve what I want to do, I make a point to never do that again”)
(14). All items are summed (negatively phrased items need to be reversed first) to arrive at a
total score (range = 0-108). The original validation study found the CAQ to have satisfactory
internal consistency and validity (14). The reliability and validity of a translated Swedish
version was tested in this study.
Committed Action Questionnaire (shortened version) (CAQ-8): The CAQ-8 has two
components, one positively phrased and one negatively phrased, with 4 items each. The total
score of the scale is 48. As the original the shortened version has strong reliability and
validity. (15).The reliability and validity of a translated Swedish version was tested in this
study.
Chronic Pain Acceptance Questionnaire (CPAQ): The CPAQ assesses another component of
the psychological flexibility model, namely acceptance, in people with chronic pain (21). This
self-report measure is comprised of 20 items rated on a 7-point scale (0 = never true; 6 =
6
always true) and includes two subscales: activity engagement and pain willingness. Higher
total and subscale scores reflects greater acceptance. The English language version of the
CPAQ has good internal reliability (α = 0.74), a stable factor structure and correlates
significantly with measures of pain-related functioning (4, 21). The Swedish version of the
CPAQ used in this study has satisfactory internal reliability (α = 0.91) and correlates well
with measures of pain functioning (16). The CPAQ was used to investigate the construct
validity of the CAQ.
Hospital Anxiety and Depression Scale (HADS): The HADS is a commonly used, 14-item
self-report measure designed to detect symptoms of anxiety and depression (separately)
amongst patients in a medical setting (22). The anxiety and depression subscales each contain
seven items rated on a four-point scale (0 to 3), with higher scores indicating greater severity.
Consistent with the English original, the Swedish version used in this study has been shown to
have excellent internal reliability for the total (α = 0.90), anxiety (α = 0.84) and depression
scales (α = 0.82) and to correlate significantly with alternate measures of anxiety and
depression (23). The HADS was used to investigate the criterion validity of the CAQ.
Medical Outcomes Study Short Form 36-Item Health Survey (SF-36): This is a self-report
measure of non-disease-specific health and functioning widely used in health research (24).
The 36 items are used to compute 8 subscales scores. The following subscales were used in
this study: physical functioning -10 items, vitality - 4 items, mental health - 5 items, social
functioning -2 items, and general health - 5 items. All subscales are transformed to a 0-100
scale with higher scores indicate a greater health state. Like the English original, the Swedish
version used in this study has been shown to have excellent internal reliability for the
subscales (α = 0.79 to 0.91) and validity when compared with other measures of health
functioning (24, 25). The SF-36 was used to investigate the criterion validity of the CAQ.
7
Psychological Inflexibility in Pain Scale (PIPS): The PIPS measures psychological
inflexibility in relation to chronic pain. It is a self-report measure with 12 items rated on a 7-
point scale (1= never true; 7 = always true) and includes two subscales cognitive fusion
related to pain and avoidance of pain. Higher scores indicate greater psychological
inflexibility and the maximum score is 84. The scale has satisfactory psychometric
properties(α = 0.87).(6) The PIPS was used to investigate the construct validity of the CAQ.
Tampa Scale of Kinesiophobia (TSK): The TSK assesses fear of (re)injury by physical
movement or activity. This self-report measure has 17 items rated on a 4-point scale (1 =
strongly disagree; 4 =strongly agree). The total score has a range from 17 to 68 and higher
scores indicate higher pain-related fear. The TSK has been shown to have satisfactory
psychometric properties (α = 0.75) and a Swedish version was used in this study.(26-28).
Statistical approach
All CAQ items were investigated for missing data and frequency distribution. Reliability was
estimated in several ways including via inter-item correlations, item-total correlations and
Cronbach’s alpha, where a score of 0.70 or higher was considered acceptable (29).
Confirmatory factor analysis (CFA) was used to investigate whether the factor structure in the
current sample matched the two-factor models found in the original validation studies. For
cross-validation purposes confirmatory factor analysis is preferred over exploratory factor
analysis since CFA tests the degree to which a hypothesized factor structure matches the
pattern of covariances among the scale´s items (30, 31). Items were considered for removal if
the corrected item-total correlation was below r= 0.30 (29) or the item loading (standardized
regression weights) was below .32. (32)The analysis was conducted using maximum
likelihood estimation and goodness of fit was evaluated by: the relative/normed Chi-Square
statistic (x2/df; acceptable fit<5) (31), Tucker–Lewis Index (TLI; acceptable fit≥ 0.95) (32),
8
the Root Mean Square Error of Approximation (RMSEA) and the Comparative Fit Index
(CFI; adequate fit > .90, good fit > .95) (33, 34). The relative/normed Chi-Square (χ2/df) was
used instead of the traditional Chi-Square value together with the associated p-value because
it reduces the likelihood of falsely rejecting the model when one has large sample sizes as in
the present study (33). RMSEA is a well-established fit statistic which can be considered one
of the most informative. Recommendations for cut-off points have varied over the years. (33,
34) Frequently reported cut-offs include “close fit” < 0.05, “reasonable fit” <.08, and
“mediocre fit” < 0.10 (35). The sample size of 462 was deemed satisfactory according to
established guidelines for factor analysis. (36-39)
Criterion validity was investigated in the form of “concurrent validity,” as all measures were
collected at the same time. Pearson correlation coefficients were calculated and all
correlations were evaluated as strong (.5- 1.0), moderate (.3-.5) or small (.1-.3).(40)
Correlation analyses of the CAQ-18 and CAQ-8 were conducted in relation to background
variables as well as the criterion variables, which included depression and anxiety (HADS)
and health and functioning (SF-36). Additional correlations between pain acceptance (CPAQ)
and the same background and criterion measures were examined to evaluate the performance
of the CAQ-18 and CAQ-8 in comparison to a well-known measure from the same
psychological flexibility model. Also, correlations between kinesiophobia (TSK) and the
same background and criterion variables were performed to be able to compare the
performance of CAQ-18 and CAQ-8 in relation to an independent construct, which is
considered highly relevant for in chronic pain.(16)
The relationships between the CAQ (CAQ-18 and CAQ-8), CPAQ and psychological
flexibility (PIPS) were also examined and can be considered tests of construct validity, since
these are theoretically related measures specified within the psychological flexibility model
and predicted to correlate. (3, 18) Regression analysis was performed to determine if CPAQ
9
and CAQ were significant contributors to PIPS, which measures psychological flexibility the
overarching process within the psychological flexibility model. According to the model
acceptance and committed action are supposed to contribute to psychological flexibility
together with four other processes. (3, 18)
To examine the incremental validity of the CAQ a series of regression analyses were
undertaken. It was investigated whether the CAQ (CAQ-18 and CAQ-8) was able to account
for variance in patient functioning over and above the effect of CPAQ and TSK. The
regression analyses were done hierarchically. For each dependent variable two models were
tested; the first included background information and CAQ only, and the second included
background information, CPAQ, TSK, and CAQ. Seven indices of patient functioning were
used as dependent variables: depression and anxiety (HADS); physical functioning, social
functioning, vitality, mental health, and general health (SF-36). The effects of background
variables (age, gender, and education) were examined for each dependent variable and
included in the regression analyses if significant at p < .01. The significant background
variables were entered first (Step 1) followed by CAQ (Step 2) in the first model. In the
second model significant background variables were entered first followed by CPAQ (Step 2),
TSK (Step 3) and CAQ (Step 4). All analyses were conducted using SPSS and AMOS
(Version 22).
Results
Descriptive and attrition analyses
Of the 462 participants 157 (34 %) had missing data, in these cases due to the patient failing
to complete a particular measure or item. In attempting to deal with missing data we adhered
to recommended statistical procedures.(41, 42) Missing values analyses indicated that data
was missing completely at random (Little’sMCAR test: Chi-square = 2024.3, df = 2015, p
10
= .438) and the average percentage of missing data in the variables was only 1.80 %.
Consequently, it was deemed suitable to keep all cases in the analyses and impute missing
values with the Expectation-maximization (EM) method. (42, 43)
Item-analysis
All 18 items of the CAQ had response rates above 97.1%. Visual inspection of histograms,
normal Q-Q plots and boxplots ensured that all items were approximately normally
distributed. Outliers (n=40) were identified by computing standardized scores using absolute
Z values larger than 3 as a cut off. The affected values of the outliers were winsorized and
consequently included in all analyses(44). The observed mean for the CAQ-18 total was 59.9
(SD = 16.4) and for the CAQ-8 was 26.3 (SD=8.5). All items correlated with each other with
no inter-item correlation above r=0.66. All item-total correlations were greater than r = .30
(range = .36 to .69), except for item 9 from the CAQ-18 (“I get stuck doing the same thing
over and over even if I am not successful”; r = .13). The observed Cronbach alphas for CAQ-
18 were α = .89 (CAQ Total), α = .90 (positively framed item factor), and α = .80 (negatively
framed item factor). The observed Cronbach alphas for CAQ-8 were α = .84 (CAQ Total), α =
.86 (positively framed item factor), and α = .77 (negatively framed item factor).
Confirmatory factor analysis
CFA was used to investigate whether the Swedish translation of the CAQ yielded similar two-
factor models as found in the original validation studies(14, 15). Fit indices are displayed in
Table 1. Taken together, these indicated either satisfactory fit for the 18 item- model
(RMSEA, CFI and x2/df) or values just short of satisfactory (TFI). Modification indices from
the initial model indicated a high level of covariance between Item 1(“I am able to persist
with a course of action after experiencing difficulties”) and Item 2 (“When I fail in reaching a
goal, I can change how I approach it”). To investigate if model fit could be improved one
11
supplementary model was tested, where the error terms of these items were allowed to covary.
This adjusted model was deemed appropriate since both items loaded on the same factor and
reflect facing difficulties and continuing with one’s commitments. Permitting this covariance
improved the model fit. For the 8 item- model all fit indices indicated satisfactory fit. Table 2
shows descriptive data and item loadings (standardized regression weights) from the CFA.
They were generally satisfactory for CAQ-18(range for Factor 1 = .55 to .79; range for Factor
2 = .47 to .76). The loading for item 9 (“I get stuck doing the same thing over and over even if
I am not successful”) on Factor 2 was again somewhat weak (.25). However, given the largely
satisfactory match between the model obtained in the current sample and the original
validation study, and the unique and highly face valid content included in this item, we
elected to retain the adjusted 18-item, two factor model. Item loadings (standardized
regression weights) for CAQ-8 were all satisfactory (range for Factor 1=.75 to.79; range for
Factor 2=.61 to .80).
Table 1 Goodness of fit indicesModel 2-factor 18
items2-factor w covaried error (item1-item2)
18 items
2-factor 8 items
x2/df 3.52 3.16 2.97TLI .89 .90 .96
RMSEA(confidence interval)
.07 (.07-.08) .07 (.06-.08) .07 (.05-.09)
CFI .90 .92 .97Notes: Godness of fit indices were: the relative/normed Chi-Square statistic(x2/df; acceptable fit<5); tucker–lewis index (TLI; acceptable fit≥ 0.95); the root mean square error of approximation (RMSEA; close fit < 0.05, reasonable fit <.08, and mediocre fit < 0.10); the comparative fit index (CFI; adequate fit > 0.90, good fit > 0.95)Similar results were obtained using the Scale-free least squares estimator, where the assumption of multivariate normality does not need to be met
12
Table 2 Descriptive data and standardized regression weights from the CFA for the 18 items in the Committed Action QuestionnaireItemno
Items Mean (sd)
CAQ-18 CAQ-8Standardized regression weights
Factor 1 (positively phrased)
Factor 2 (negatively
phrased)
Factor1 (positively phrased)
Factor 2 (negatively
phrased) 1 I am able to persist with a course of action
after experiencing difficulties3.15 (.72)
.55
2 When I fail in reaching a goal, I can change how I approach it
3.66 (1.56)
.73
3 (1) I can remain committed to my goals even when there are times that I fail to reach them
3.59 (1.47)
.79 .78
4 (2) When a goal is difficult to reach, I am able to take small steps to reach it
3.77 (1.50)
.79 .81
6 (3) I prefer to change how I approach a goal rather than quit
3.89 (1.49)
.72 .75
7 (4) I am able to follow my long term plans including times when progress is slow
3.65 (1.54)
.77 .79
12 I am able to pursue my goals both when this feels easy and when it feels difficult
3.27 (1.55)
.77
13 I am able to persist in what I am doing or to change what I am doing depending on what helps me reach my goals
3.61 (1.38)
.68
15 I am able to incorporate discouraging experiences into the process of pursuing my long term plans
4,01 (1.36)
.62
5 I act impulsively when I feel under pressure
2.65 (1.69)
.47
8 When I fail to achieve what I want to do, I make a point to never do that again
3.68 (1.60)
.51
9 I get stuck doing the same thing over and over even if I am not successful
3.64 (1.50)
.25
10 (5) I find it difficult to carry on with an activity unless I experience that it is successful
2.53 (1.59)
.64 .61
11 I am more likely to be guided by what I feel than by my goals
2.58 (1.49)
.60
14 If I make a commitment and later fail to reach it, I then drop the commitment
3.33 (1.50)
.49
16 (6) If I feel distressed or discouraged, I let my commitments slide
2.39 (1.51)
.70 .71
17 (7) I get so wrapped up in what I am thinking or feeling that I cannot do the things that matter to me
2.91 (1.67)
.76 .80
18 (8) If I cannot do something my way, I will not do it at all
3.59 (1.63)
.62 .62
Notes: The CFA was conducted using maximum likelihood estimation.
13
Factor 1consists of nine positively phrased items and Factor 2 of nine negatively phrased items in the model for CAQ-18Factor 1consists of four positively phrased items and Factor 2 of four negatively phrased items in the model for CAQ-8
Relationship with background and criterion variables
Table 3 presents correlations between the CAQ, background and criterion variables.
Significant correlations were found between the CAQ and all criterion variables (range for
CAQ-18 r=.20-.48, p < .01; range for CAQ-8 r=.16-.47, p < .01). Generally, the associations
were in line with the expectations made in the a priori hypotheses. The correlations between
the CAQ and the criterion/background variables were of comparable magnitude to both those
between the same background/criterion variables and Swedish language versions of the
CPAQ and the TSK. The correlation between the CAQ-18 and the TSK was r=-.35 (p< .01),
the correlation between CAQ-8 and the TSK was r=-.31(p< .01) and the correlation between
the CPAQ and the TSK was r=-.44 (p< .01)
Table 3 Correlations with background and criterion variablesCommitted action
(CAQ-18)Committed action
(CAQ-8)Pain acceptance Kinesiophobia
Background variables
Age -.02 -.04 .04 -.19**Gender .09* .10* .19** .12**
Education .20** .16* .20** -.23**Criterion variables
Depression -.48** -.47** -.54** .37**Anxiety -.47** -.45** -.41** .40**Physical
functioning.20** .16** .27** -.41**
Social functioning
.28** .30** .56** -.27**
Mental health .46** .46** .50** -.44**Vitality .24** .26** .37** -.20**
General health .35** .34** .32** -.40**
14
Notes: Pain acceptance was measured with the Chronic Pain Acceptance Questionnaire, committed action with the Committed Action Questionnaire, kinesiophobia with Tampa Scale of Kinesiophobia, depression and anxiety with the Hospital Anxiety and Depression Scale. Physical functioning, social functioning, mental health, vitality and general health were measured with The Medical Outcomes Study Short Form 36-Item Health Survey *P < .05.**P < .01
Regression analyses
When investigating construct validity the correlations were consistent with the relationships
hypothesized a priori. The correlation between the CAQ-18 and the CPAQ was r=.37
(p< .01), the correlation between the CAQ-18 and the PIPS was r=-.48, p< .01) and the
correlation between the CPAQ and the PIPS was r=-.70. The correlations for CAQ-8 and
CPAQ was as r=.35 (p< .01) and the correlation between CAQ-8 and PIPS was r=-.45, p< .01.
The contribution of pain acceptance and committed action to psychological flexibility was
investigated with regression analysis. Using PIPS as a dependent variable, CPAQ and CAQ-
18explained 55 % of the variance (R=.74, R2=.55, Beta (CPAQ)=-.61, t(CPAQ)=-17.95 (p
< .001); Beta(CAQ)=-.25, t(CAQ)=-7.48 (p < .001). The regression analysis was repeated
with CAQ-8 instead of CAQ-18 with similar results.
With regard to incremental validity table 4 presents the results of the hierarchical regression
analyses. In the first step, age, gender and education were examined in relation to each of the
dependent variables (indices of functioning). Background variables were retained in the
subsequent regressions involving that dependent variable if they were found significant. In the
regression models including significant background information and CAQ-18, the CAQ-18
accounted for a significant proportion of the variance in functioning (range 3% to 21%) in six
out of six models. In the regression models including CPAQ, TSK and CAQ-18 as
independent variables, the CAQ-18 accounted for a significant proportion of the variance in
functioning (range = 1% to 8%) in five out of six models. No significant contribution was
15
shown in the equation for physical functioning. The same regression analyses were conducted
with CAQ-8 instead of CAQ-18. The shortened version explained as much or more variance
in the analyses.
All relationships between the CAQ and the dependent variables were in the expected
direction; higher levels of committed action were associated with lower depression and
anxiety and better health and functioning. The total explained variance (R2) was relatively
large in several models with more than 30% of the variance in depression, anxiety, social
functioning and mental health explained by pain acceptance, kinesiophobia and committed
action.
16
Table 4 Hierarchical regression analyses of patient functioning in relation to pain acceptance and committed action (CAQ-18)
Dependent variable
Block Predictor R R2 R2
changeβ
(final)t
Depression 1 AgeEducation
.20 .04 .04 .12** 2.92-.06 -1.48
2 Committed action .50 .25 .21 -.47** -11.261 Age
Education.20 .04 .04 .09* 2.45
.00 .062 Pain acceptance .55 .30 .26 -.37** -9.293 Kinesiophobia .56 .32 .02 .08 1.774 Committed action .63 .40 .08 -.31** -7.71
Anxiety 1 Education .20 .04 04 -.12** -2.752 Committed action .48 .23 .19 -.45** -10.641 Education .20 .04 04 -.06 -1.502 Pain acceptance .42 .18 .14 -.19** -4.323 Kinesiophobia .48 .23 .05 .19** 4.134 Committed action .56 .31 .08 -.32** -7.42
Physical functioning
1 AgeEducation
.31 .09 .09 -.26** 3.29.15** -5.81
2 Committed action .35 .12 .03 .17** 3.731 Age
Education.31 .09 .09 -.21** -5.02
.08 1.902 Pain acceptance .38 .14 .05 .09 1.943 Kinesiophobia .47 .22 .07 -.31** -6.384 Committed action .47 .22 .00 .04 .85
Social functioning 1 Committed action .28 .08 .08 .28** 6.331 Pain acceptance .56 .31 .31 .52** 11.752 Kinesiophobia .56 .31 .00 -.01 -.323 Committed action .57 .32 .01 .09* 2.06
Mental health 1 Education .15 .02 .02 .06 1.422 Committed action .46 .21 .19 .44** 10.461 Education .15 .02 .02 -.01 -.342 Pain acceptance .50 .25 .23 .31** 7.243 Kinesiophobia .56 .31 .06 -.21** -4.894 Committed action .61 .37 .06 .27** 6.53
Vitality 1 Committed action .24 .06 .06 .24** 5.271 Pain acceptance .37 .14 .14 .32** 6.412 Kinesiophobia .37 .14 .00 -.02 -.463 Committed action .39 .15 .01 .11* 2.40
General health 1 Committed action .35 .12 .12 .35** 7.881 Pain acceptance .32 .10 .10 .12* 2.542 Kinesiophobia .43 .18 .08 -.27** -5.793 Committed action .47 .22 .03 .20** 4.47
17
Notes: Two models were tested for all dependent variables. One included background variables and committed action, and the other included background variables, pain acceptance, kinesiophobia and committed action. Pain acceptance was measured with the Chronic Pain Acceptance Questionnaire, committed action with the Committed Action Questionnaire, kinesiophobia with Tampa Scale of Kinesiophobia, depression and anxiety with the Hospital Anxiety and Depression Scale. Physical functioning, social functioning, mental health, vitality and general health were measured with The Medical Outcomes Study Short Form 36-Item Health Survey *p < .05**P < .01
Discussion
Psychological flexibility as a model concerns itself with the capacity to persist with or change
behavior to serve one´s goals in a context of psychological influence and situational prospects
(14). As applied to chronic pain, the model emphasizes helping patients to take actions that
are consistent with their personal goals and contribute to their overall wellbeing and
functioning. Within this model these actions are meant to have certain qualities, they are done
with openness and awareness of experiences such as pain, anxiety or depression, while at the
same time not unduly governed by these experiences. One specific element within this model
is committed action, conceptualized essentially as flexible, sensitive, behavioral persistence.
Recently, an 18-item English language measure of committed action was developed – the
Committed Action Questionnaire (CAQ).(14) A shortened version (CAQ-8) has also been
developed.(15) The purpose of the present study was to validate the original and the shortened
version of the CAQ in Swedish, to examine the generality of previous results related to
committed action and to further demonstrate the relevance of this construct to the functioning
of patients with chronic pain.
All a priori hypotheses in the study were supported and the translated versions of the CAQ
were found to have satisfactory psychometric properties in the sample of Swedish chronic
pain patients examined in this study. First, both versions of the CAQ yielded high levels of
internal consistency and reliability. Second, we were able to retain all items of the measures
and fit the two factor models, suggested in the original validation studies, to the observed data
with only the slightest modification. Third, taken together the CAQ demonstrated good
18
concurrent validity. Pair-wise correlations between these versions of the CAQ and various
background variables and indices of patient functioning were generally significant and of the
expected magnitudes. The magnitudes of the correlations were also comparable to those
between the Swedish language version of the CPAQ and the TSK and these same
background/criterion variables. Fourth, the significant correlations with the theoretically-
related measures of pain acceptance and psychological flexibility provided support for the
construct validity of the CAQ. Furthermore, the CAQ was identified a significant contributor
to psychological flexibility, the overarching process within the psychological flexibility
model. Finally, hierarchical regression analyses supported the incremental validity of the
CAQ since it was shown that the measure made a significant contribution to explaining the
variance in overall functioning, particularly depression and anxiety, after accounting for the
contribution of pain acceptance and kinesiophobia. All in all, these findings provide
preliminary support for the validity of the Swedish language versions of the CAQ, support the
reliability and generality of the earlier findings to another context, support the relevance of
this construct to the functioning of patients with chronic pain and further support the notion
that the various components of psychological flexibility work together to help explain
functioning in pain patients.
The findings from this study are in line with a large number of studies that have shown that
key processes identified in the psychological flexibility model are significantly related to the
functioning of people with chronic pain (8-13, 45). Further, they strengthen earlier findings
with regard to the relatively newly researched facet of psychological flexibility, i.e.,
committed action (14, 15, 17, 46). Currently, all six key processes of psychological flexibility
have empirical support within the field of chronic pain. Specifically, acceptance (4, 8-10, 16,
45, 47-60) and value-based action (7, 9, 57, 61-63) have strong empirical support, and the
19
less studied processes of committed action (14, 15, 17, 64), present-focused awareness (9, 61,
65), cognitive defusion (6, 12) and self-as-observer (66) have all received preliminary
support in explaining functioning in pain patients. The development and further validation of
the CAQ is an important step forward in evaluating the utility of the psychological flexibility
model to the treatment of chronic pain. Much of the previous research into psychological
flexibility has focused on the openness and awareness components, and less on the activation,
engagement, goals, and motivation components, which can now be more fully addressed (15,
18). Future studies will need to further examine these less studied processes, including within
different national contexts and cultures.
Current psychological treatments for chronic pain only produce small to medium effect sizes.
Hence, these treatments can be improved. Up until now studies have not revealed which
processes and methods are most effective or necessary in improving outcome. Identification
of “active processes” or mediators of outcome could be used to refine treatments (67, 68). The
psychological flexibility model, including committed action, has been identified as a potential
framework for understanding change processes during chronic pain treatment. It has been
argued that its theoretical base, philosophical principles and scientific strategy could guide
future research activity in a consistent fashion A major strength of the model is that it
specifies six processes (mediators) which facilitate change during treatment(18). One of these
processes is committed action. Consequently, the development and translation of the CAQ
can assist researchers interested in treatment development through identification of mediators
of chronic pain treatment, and particularly mediators based in the psychological flexibility
model. Additionally, it can help clinicians when assessing the strength and workability of
their interventions and treatment programs during or after treatment.
Findings from the present study must be viewed within the context of certain limitations. All
findings are based on patient self-reports obtained at one point in time and without reference
20
to a control group. Second, the while the obtained results were similar to the original
validation studies, the findings from all these studies are based on chronic patients seeking
treatment from highly specialist pain services and results may not generalize to other samples.
(14, 15) Third, the present sample was comprised primarily by women with a high percentage
of participants having university-level education. While this may make the sample less
representative of chronic pain patients generally, we note that the unique quality of the current
sample and its dissimilarity to the samples included in the original validation studies of the
CAQ lend greater support for the generality of the findings. (14, 15) Fourth, the variance in
functioning accounted for by the CAQ varied greatly across the measures of functioning and
one relation was non-significant (physical functioning). Future controlled longitudinal studies
are needed to clarify the relative contribution of committed action to functioning and
treatment outcome. Fifth, all relevant psychometric properties have not been investigated in
this study. Future studies could complement the analyses by examining sensitivity to change
and other validity indicators.
A final caveat is worth mentioning. The six processes specified in psychological flexibility,
including committed action, represent current tools for further investigation and clinical
development. While they are abstracted or translated to a degree from a set of basic
behavioral principles, mostly from within contextual behavioral research, they are not
themselves precise technical terms directly generated from experimental laboratories. They
are often referred to a “midlevel” terms as their function is to link the language of clinicians to
the language of basic researchers (3). It is important for future progress that these terms not be
reified and to recognize that one day these will appear limited and will likely change.
In sum, this study supports the validity and reliability of these Swedish language versions of
the CAQ, the generality of the earlier findings and the relevance of committed action to
21
functioning in chronic pain patients. The CAQ may be a useful tool for investigating
mediators or “active” processes of change in treatment for chronic pain.
Acknowledgements
We are grateful to Katarina Lundberg and the psychologists at the Department of Pain
Rehabilitation, Skåne University Hospital for their contributions during the measure
translation.
Ethical approval
All procedures performed in this study were in accordance with the ethical standards of the
institutional and/or national research committee and with the 1964 Helsinki declaration and its
later amendments or comparable ethical standards.
Funding
No funding sources were provided.
Conflicts of interest
The authors declare that they have no conflict of interest.
22
References
1. Hann KE, McCracken LM. A systematic review of randomized controlled trials of Acceptance and Commitment Therapy for adults with chronic pain: Outcome domains, design quality, and efficacy. Journal of Contextual Behavioral Science. 2014;3(4):217-27. 2. Hayes SC, Strosahl K, Wilson KG. Acceptance and commitment therapy : an experiential approach to behavior change. New York ; London: Guilford Press; 1999.3. Hayes SC, Strosahl KD, Wilson KG. Acceptance and Commitment Therapy: The Process and Practice of Mindful
Change. London: Guilford Press; 2012.4. Vowles KE, McCracken LM, McLeod C, Eccleston C. The Chronic Pain Acceptance Questionnaire: Confirmatory factor analysis and identification of patient subgroups. Pain. 2008;140(2):284-91. doi:10.1016/j.pain.2008.08.0125. Brown KW, Ryan RM. The benefits of being present: mindfulness and its role in psycholological well-being. Jornal of Personality and Social Psychology. 2003;84(1):822-48. 6. Wicksell RK, Lekander M, Sorjonen K, Olsson GL. The Psychological Inflexibility in Pain Scale (PIPS) - Statistical properties and model fit of an instrument to assess change processes in pain related disability. European Journal of Pain. 2010;14(7):771.e1–.e14. 7. McCracken LM, Yang SY. The role of values in a contextual cognitive-behavioral approach to chronic pain. Pain. 2006;123(1-2):137-45. doi:10.1016/j.pain.2006.02.0218. Baranoff J, Hanrahan SJ, Kapur D, Connor JP. Acceptance as a process variable in relation to catastrophizing
in multidisciplinary pain treatment. European Journal of Pain. 2013; 17:101–10 doi:10.1002/j.1532-2149.2012.00165.x9. Vowles KE, Wetherell JL, Sorrell JT. Targeting Acceptance, Mindfulness, and Values-Based Action in Chronic Pain: Findings of Two Preliminary Trials of an Outpatient Group-Based Intervention. Cognitive and Behavioral Practice. 2009;16(1):49-58. doi:10.1016/j.cbpra.2008.08.00110. McCracken LM, Gutiérrez-Martínez O. Processes of change in psychological flexibility in an interdisciplinary group-based treatment for chronic pain based on Acceptance and Commitment Therapy. Behaviour Research and Therapy. 2011;49(4):267-74. doi:10.1016/j.brat.2011.02.00411. Vowles KE, Witkiewitz K, Sowden G, Ashworth J. Acceptance and commitment therapy for chronic pain: Evidence of mediation and clinically significant change following an abbreviated interdisciplinary program of rehabilitation. The Journal of Pain. 2014;15(1):101-13. doi:10.1016/j.jpain.2013.10.00212. Wicksell RK, Olsson GL, Hayes SC. Psychological flexibility as a mediator of improvement in Acceptance and Commitment Therapy for patients with chronic pain following whiplash. European Journal of Pain. 2010;14(10):1059.e1-.e11. doi:10.1016/j.ejpain.2010.05.00113. Åkerblom S, Perrin S, Rivano Fischer M, McCracken LM. Original Report: The Mediating Role of Acceptance in Multidisciplinary Cognitive-Behavioral Therapy for Chronic Pain. Journal of Pain. 2015. doi:10.1016/j.jpain.2015.03.007
23
14. McCracken LM. Committed action: An application of the psychological flexibility model to activity patterns in chronic pain. Journal of Pain. 2013;14 (8):828-35. doi:10.1016/j.jpain.2013.02.00915. McCracken LM, Chilcot J, Norton S. Further development in the assessment of psychological flexibility: A shortened committed action questionnaire (caq 8). European Journal of ‐Pain. 2014. doi:doi: 10.1002/ejp.58916. Wicksell RK, Olsson GL, Melin L. The Chronic Pain Acceptance Questionnaire (CPAQ)-further validation including a confirmatory factor analysis and a comparison with the Tampa Scale of Kinesiophobia. European Journal of Pain. 2009;13(7):760-8. doi:10.1016/j.ejpain.2008.09.00317. Wong W-s, McCracken L, Wong S, Chen P-p, Chow Y-f, Fielding R. The Chinese Version of the 8-Item Committed Action Questionnaire (ChCAQ-8): A Preliminary Analysis of the Factorial and Criterion Validity. Psychological Assessment. 2015. doi:10.1037/pas0000187
10.1037/pas0000187.supp (Supplemental)18. McCracken LM, Morley S. The psychological flexibility model: A basis for integration and progress in psychological approaches to chronic pain management. Journal of Pain. 2014;15(3):221-34. doi:10.1016/j.jpain.2013.10.01419. Rehabilitation SQRfP. Årsrapport 2015 (Internet). Swedish Quality Registry for Pain Rehabilitation. 2015. http://www.ucr.uu.se/nrs/index.php/arsrapporter. Accessed Sep 25th 2015.20. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine. 2000;25(24): 3186-91. 21. McCracken LM, Vowles KE, Eccleston C. Acceptance of chronic pain: Component analysis and a revised assessment method. Pain. 2004;107(1-2):159-66. doi:10.1016/j.pain.2003.10.01222. Zigmond AS, Snaith RP. The Hospital Anxiety and Depression Scale. Acta Psychiat Scand. 1983;67(6):361-70. doi:DOI 10.1111/j.1600-0447.1983.tb09716.x23. Lisspers J, Nygren A, Soderman E. Hospital Anxiety and Depression Scale (HAD): some psychometric data for a Swedish sample Acta Psychiat Scand. 1997; 96 281-6. 24. Ware JE, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36): I. Conceptual Framework and Item Selection. Medical Care. 1998;36(5):752-6. 25. Sullivan M, Karlsson J, Ware Jr JE. The Swedish SF-36 Health Survey-I. Evaluation of data quality, scaling assumptions, reliability and construct validity across general populations in Sweden. Social Science and Medicine. 1995;41(10):1349-58. 26. Swinkels-Meewisse EJ, Roelofs, J., Verbeek, A.L.M., Oostendorp, R.A.B., Vlaeyen, J.W.S. . Fear of movement/(re)injury, disability and participation in acute low back pain. Pain. 2003;105 371–9.
27. Vlaeyen JWS, Kole-Snijders, A.M.J. ., Boeren, R.G.B., Van Eek, H. . Fear of movement/ (re)injury in chronic low back pain and its relation to behavioral performance. Pain. 1995;62 363–72. 28. Roelofs J SJ, Frings-Dresen MH, Goossens M, Thibault P, Boersma K, Vlaeyen JW. Fear of movement and (re)injury in chronic musculoskeletal pain: Evidence for an invariant two-factor model of the Tampa Scale for Kinesiophobia across pain diagnoses and Dutch, Swedish, and Canadian samples. Pain. 2007 131(1-2):181-90. 29. Nunnally J, Bernstein I. Psychometric Theory,. 3
ed. New York, NY: McGraw Hill; 1994.30. Watkins D. The role of confirmatory factor analysis in cross-cultural research. International Journal of Psychology. 1989;24(6):685-701. 31. van Prooijen J, van der Kloot WA. Confirmatory Analysis of Exploratively Obtained Factor Structures. Educational and Psychological Measurement. 2001;61(5):777-92. 32. Tabachnick BG, Fidell LS. Using multivariate statistics / Barbara G. Tabachnik, Linda S. Fidell: Boston, Mass. ; London : Pearson Education, cop. 2013
24
6th ed.; 2013.33. Hooper D, Coughlan J, Mullen MR. Structural Equation Modelling: Guidelines for Determining Model Fit. Electronic Journal of Business Research Methods. 2008;6(1):53-9. 34. Hu LT, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives. Structural Equation Modeling. 1999;6(1):1-55. doi:10.1080/1070551990954011835. MacCallum RC, Browne MW, Sugawara HM. Power analysis and determination of sample size for covariance structure modeling. Psychological Methods. 1996;1(2):130-49. doi:10.1037/1082-989X.1.2.13036. Mundfrom DJ, Shaw DG, Tian Lu K. Minimum Sample Size Recommendations for Conducting Factor Analyses. International Journal of Testing. 2005;5(2):159-68. doi:10.1207/s15327574ijt0502_437. Costello AB, Osborne JW. Best practices in exploratory factor analysis: Four recommendations for getting the most from your analysis. Practical Assessment, Research and Evaluation. 2005;10(7). 38. Kline P. An easy guide to factor analysis. New York: Routledge; 1994.39. Gorsuch R. Factor Analysis. 2nd ed. Hillsdale, NJ: Erlbaum1983.40. Cohen J. Statistical power analysis for the behavioral sciences 2nd edition ed. Mahwah, NJ: Erlbaum; 1988.41. Little RJ, D'Agostino R, Cohen ML, et al. The prevention and treatment of missing data in clinical trials. The New England Journal of Medicine. 2012;367(14):1355-60. 42. Dziura JD, Post LA, Zhao Q, Fu Z, Peduzzi P. Strategies for dealing with missing data in clinical trials: from design to analysis. The Yale Journal Of Biology And Medicine. 2013;86(3):343-58. 43. Schafer JL, Graham JW. Missing data: Our view of the state of the art. Psychological Methods. 2002;7(2):147-77. doi:10.1037/1082-989X.7.2.14744. Hawkins DM. Identification of outliers. London: Chapman & Hall.1980.45. McCracken LM, Eccleston C, Vowles KE. Acceptance-based treatment for persons with complex, long standing chronic pain: A preliminary analysis of treatment outcome in comparison to a waiting phase. Behaviour Research and Therapy. 2005;43(10):1335-46. doi:10.1016/j.brat.2004.10.00346. Trompetter HR, ten Klooster PM, Schreurs KMG, Fledderus M, Westerhof GJ, Bohlmeijer ET. Measuring values and committed action with the Engaged Living Scale (ELS): Psychometric evaluation in a nonclinical sample and a chronic pain sample. Psychological Assessment. 2013;25(4):1235-46. doi:10.1037/a003381347. Baranoff J, Hanrahan S, Kapur D, Connor J. Validation of the Chronic Pain Acceptance Questionnaire-8 in an Australian Pain Clinic Sample. International Journal of Behavioral Medicine. 2014;21(1):177-85. doi:10.1007/s12529-012-9278-648. Bendayan R, Esteve R, Blanca MJ. New empirical evidence of the validity of the Chronic Pain Acceptance Questionnaire: The differential influence of activity engagement and pain willingness on adjustment to chronic pain. British Journal of Health Psychology. 2012;17(2):314-26. doi:10.1111/j.2044-8287.2011.02039.x49. Costa J, Pinto-Gouveia J. Acceptance of pain, self-compassion and psychopathology: Using the Chronic Pain Acceptance Questionnaire to identify patients' subgroups. Clinical Psychology & Psychotherapy. 2011;18(4):292-302. doi:10.1002/cpp.71850. Fish RA, McGuire B, Hogan M, Stewart I, Morrison TG. Validation of the Chronic Pain Acceptance Questionnaire (CPAQ) in an Internet sample and development and preliminary validation of the CPAQ-8. Pain. 2010;149(3):435-43. doi:10.1016/j.pain.2009.12.01651. Hayes SC, Bissett RT, Korn Z, et al. The Impact of Acceptance Versus Control Rationales on Pain Tolerance. Psychological Record. 1999;49(1):33-47. 52. McCracken LM. Learning to live with the pain: acceptance of pain predicts adjustment in persons with chronic pain. Pain. 1998;74(1):21-7.
25
53. Mesgarian F, Asghari A, Shaeiri MR, Broumand A. The Persian Version of the Chronic Pain Acceptance Questionnaire. Clinical Psychology & Psychotherapy. 2013;20(4):350-8. doi:10.1002/cpp.176954. Monticone M, Ferrante S, Rocca B, Nava T, Parini C, Cerri C. Chronic Pain Acceptance Questionnaire Confirmatory Factor Analysis, Reliability, and Validity in Italian Subjects With Chronic Low Back Pain. Spine. 2013;38(13):E824-E31. 55. Ning MC, Ming TWC, Mae JYC, Ping CP. Validation of the Chronic Pain Acceptance Questionnaire (CPAQ) in Cantonese-Speaking Chinese Patients. Journal of Pain. 2008;9(9):823-32. doi:10.1016/j.jpain.2008.04.00556. Vowles KE, McCracken LA, Eccleston C. Patient functioning and catastrophizing in chronic pain: The mediating effects of acceptance. HEALTH PSYCHOLOGY. 2008;27(2):S136-S43. 57. Vowles KE, McCracken LM. Acceptance and values-based action in chronic pain: A study of treatment effectiveness and process. Journal of Consulting and Clinical Psychology. 2008;76(3):397-407. doi:10.1037/0022-006X.76.3.39758. Vowles KE, McCracken LM, Eccleston C. Processes of change in treatment for chronic pain: The contributions of pain, acceptance, and catastrophizing. European Journal of Pain. 2007;11(7):779-87. doi:10.1016/j.ejpain.2006.12.00759. Vowles KE, McNeil DW, Gross RT, et al. Effects of pain acceptance and pain control strategies on physical impairment in individuals with chronic low back pain. Behavior Therapy. 2007;38(4):412-25. doi:10.1016/j.beth.2007.02.00160. Wright MA, Wren AA, Somers TJ, et al. Pain Acceptance, Hope, and Optimism: Relationships to Pain and Adjustment in Patients With Chronic Musculoskeletal Pain. The Journal of Pain. 12(11):1155-62. 61. McCracken LM, Keogh E. Acceptance, Mindfulness, and Values-Based Action May Counteract Fear and Avoidance of Emotions in Chronic Pain: An Analysis of Anxiety Sensitivity. Journal of Pain. 2009;10(4):408-15. doi:10.1016/j.jpain.2008.09.01562. Páez-Blarrina M, uciano C, Valdivia S, Gutiérrez-Martínez O, Ortega J, Rodríguez-Valverde M. The role of values with personal examples in altering the functions of pain: Comparison between acceptance-based and cognitive-control-based protocols. Behaviour Research and Therapy. 2008;46(1):84-97. doi:10.1016/j.brat.2007.10.00863. McCracken LM, Vowles KE. A Prospective Analysis of Acceptance of Pain and Values-Based Action in Patients With Chronic Pain. Health Psychology. 2008;27(2):215-20. doi:10.1037/0278-6133.27.2.21564. Trompetter HR, ten Klooster PM, chreurs KMG, Fledderus M, Westerhof GJ, Bohlmeijer ET. Measuring values and committed action with the Engaged Living Scale (ELS): Psychometric evaluation in a nonclinical sample and a chronic pain sample. Psychological Assessment. 2013;25(4):1235-46. doi:10.1037/a003381365. McCracken LM, Gauntlett-Gilbert J, Vowles KE. The role of mindfulness in a contextual cognitive-behavioral analysis of chronic pain-related suffering and disability. Pain. 2007;131(1-2):63-9. doi:10.1016/j.pain.2006.12.01366. McCracken LM, Gutiérrez-Martínez O, Smyth C. “Decentering” reflects psychological flexibility in people with chronic pain and correlates with their quality of functioning. Health Psychology. 2013;32(7):820-3. doi:10.1037/a002809367. Williams AC, Eccleston C, Morley S. Psychological therapies for the management of chronic pain (excluding headache) in adults. The Cochrane database of systematic reviews. 2012;11:CD007407. doi:10.1002/14651858.CD007407.pub368. Turner JA, Holtzman S, Mancl L. Mediators, moderators, and predictors of therapeutic change in cognitive-behavioral therapy for chronic pain. Pain. 2007;127(3):276-86. doi:10.1016/j.pain.2006.09.005
26