Effectiveness of an online self-help intervention for chronic pain based on Acceptance & Commitment Therapy (ACT) and mindfulness.

Multidimensional Pain Inventory – subscale pain interference (MPI – interference) (Kerns et al., 1985; Lousberg et al., 1999): The Multidimensional Pain Inventory was developed to assess various aspects of chronic pain and disability (Kerns et al, 1985). The subscale pain interference focuses on a psychosocial aspect of chronic pain: the interference in daily life due to pain. The scale consists of 11 items measuring pain interference in daily life with work, homework chores and social activities. All items can be answered on a 7-point Likert scale, higher scores indicating more interference. The MPI has been translated into Dutch and was validated thoroughly (Lousberg et al., 1999).

1. Hospital Anxiety Depression Scale (Zigmond & Snaith, 1983): The HADS measures presence and severity of anxiety and depressive symptoms. The scale consists of 14 items in total, 7 for each subscale. Answering categories range from 0 (‘not at all’) to 4 (‘very often’). A summed score can be achieved ranging from 0 – 21 for both subscales separately. Concurrent validity of the HADS-A is very good and the measure has good internal consistencies (Zigmond & Snaith, 1983; Spinhoven et al., 1997);

2. Mental health Continuum – Short Form (MHC-SF) (Keyes et al., 2005; Lamers Westerhof, ten Klooster & Keyes, 2010): The MHC-SF is a 14-item questionnaire that measures three dimension of positive mental health (Keyes, 2002): emotional well-being (3), defined in terms of positive feelings and satisfaction with life; psychological well-being (6), defined in terms of positive functioning in individual life (self-realization); social well-being (5), defined in terms of positive functioning in community life (being of social value). Participants are asked to rate the frequency of feelings they have experienced in the past month. Items are scored on a 6-point scale ranging from ‘never’ to ‘every day. Higher scores indicate better well-being. The Dutch version of the MHC-SF has shown good construct validity and test-retest reliability in the general adult population (Lamers et al., 2010);

3. Pain Disability Index (PDI) (Pollard, 1984): The PDI is an instrument developed to assess the degree to which chronic pain disables a person to perform daily activities (Tait, Chibnall & Krause, 1990). Seven items regarding various activities are rated by the participants on a 0-10 point scale ranging from ‘no disability’ to ‘total disability’. Several studies support the reliability and validity of the PDI (e.g. Tait et al., 1990);

4. Pain intensity – Numeric Rating Scale (NRS): Pain intensity is measured with a 11-point numeric rating scale, ranging from ‘no pain’ (0) to ‘pain as bad as you can imagine’ (10). The exact format of this rating will be as is recommended in the last IMMPACT recommendations on core outcome measures in chronic pain research (Dworkin et al., 2005);

5. Five Facet Mindfulness Questionnaire – Short Form (FFMQ-SF) (Baer, Smith, Hopkins, Krietemeyer & Toney, 2006; Bohlmeijer, ten Klooster, Fledderus, Veehof & Baer, 2011): The FFMQ-SF is a 24-item questionnaire that, just like the full 39-item FFMQ, measures five facets of mindfulness: observing, describing, acting with awareness, nonjudging and nonreactivity (Baer, Smith, Hopkins, Krietemeyer, & Toney, 2006). All items are scored on a 5-point Likert-type scale ranging from ´never or rarely true´ (1) to ´very often or always true´ (5). Higher scores indicate more mindfulness. The Dutch FFMQ was developed by translation and back-translation of the original FFMQ and has shown adequate construct validity and test-retest reliability in patients with fibromyalgia (Veehof, ten Klooster, Taal, Westerhof & Bohlmeijer, 2011). The recently developed short form also show good model fit and reliability (Bohlmeijer et al., 2011);

6. Psychological inflexibility in Pain Scale (PIPS) (Wicksell et al, 2010; Trompetter et al., in preparation): The PIPS is a 12-item instrument measuring psychological inflexibility, the main concept in Acceptance and Commitment Therapy (Hayes et al., 2006). The scale consists of two subscales measuring avoidance (8 items) and cognitive fusion (4 items). All items have to be scored by participants on a 7-point Likert-type scale ranging from ´never true´ (1) to ´always true´ (7). Higher scores indicate greater psychological inflexibility. A recent study showed good model fit, good internal consistencies, and correlations with several related constructs (such as pain disability, life satisfaction and acceptance) ((Wicksell et al., 2010). The Dutch version of the PIPS also has good validity and reliability (Trompetter et al., in preparation);

7. Twente Values Scale (TVS): The TVS is recently developed at the Unversity of Twente from an ACT-perspective to measure values-based living, a core process of ACT. The scale consists of three subscales: ‘knowing personal values’, ‘living in accordance with personal values/committed action’ and ‘general evaluation of values-based life’. Every item can be answered on a 5-point Likert scale ranging from ‘not true at all’ (1) to ‘very much true’ (5). Preliminary analysis shows the TVS has good internal consistency and good construct validity;

8. Pain Catastrophizing Scale (PCS) (Sullivan, Bishop & Pivik, 1995; Crombez & Vlaeyen, 1996): The PCS is a 13-item questionnaire developed to measure pain catastrophizing. The scale consists of three subscales measuring ‘rumination’ (4 items), ‘magnification’ (3 items) and ‘helplessness’ (6 items). Answers can be given on a 5-point Likert Scale, ranging from ‘never’ (0) to ‘always’ (4). Item scores can be summed to a total score or can be calculated for the subscales separately. Internal consistency, test-retest reliability and construct validity are all good.