Mindfulness based interventions, particularly Mindfulness-Based Stress Reduction (MBSR1
; Kabat-Zinn, 1990
) are increasingly popular. There is substantial evidence that MBSR improves mental and physical health compared to wait-list controls and treatment as usual, and is of comparable efficacy to other psychological interventions (e.g., Barnhofer et al., 2007
; Davidson et al., 2003
; Gregg, Callaghan, Hayes, & Glenn-Lawson, 2007
; Kabat-Zinn et al., 1998
; Ma & Teasdale, 2004
; Pradhan et al., 2007
; Speca, Carlson, Goodey, & Angen, 2000
). However, a complete understanding of the mechanisms by which MBSR is efficacious for these outcomes and a valid test of mindfulness as the presumed active ingredient is not currently possible due to the lack of a suitable control intervention. The validation of such a control is the subject of this article.
A direct test of the efficacy of MBSR’s active ingredients requires a comparison of MBSR to an active control that matches MBSR in non-specific factors (e.g., structure) but does not contain mindfulness as an active ingredient (Grunbaum, 1986
; Kirsch, 2005
). There are only two studies involving MBSR-like interventions that use control conditions that approach this standard (Grossman, Tiefenthaler-Gilmer, Raysz, & Kesper, 2007
; McMillan, Robertson, Brock, & Chorlton, 2002
. McMillan and colleagues randomly assigned 145 people with traumatic brain injury either to “Attention Control Training” (based on Kabat-Zinn’s work but not MBSR), physical exercise, or a wait-list control and found no differences between the two active groups. Limited descriptions of interventions and providers make it difficult to evaluate if the control was adequate.
Grossman and colleagues assigned participants with fibromyalgia to MBSR (n=43) or social support/relaxation (n=15). MBSR participants improved relative to the control group on measures of anxiety, depression, quality of life, and pain regulation. However, the study was quasi experimental and the control condition was subject to several limitations that are common in studies evaluating specific components of behavioral interventions (Wampold et al., 1997
). Specifically, patients received less contact with providers in the control condition than in the MBSR condition. In addition, the control conditions appeared to be defined more by proscriptions (e.g., “emphasis was placed upon not describing or training mindfulness skills to the control group”), rather than the skillful provision of common therapeutic elements, which may bias tests of intervention effects (Mohr et al. 2005).
An appropriate test of mindfulness as an active ingredient requires a control condition that attends to three major limitations typical of active controls in behavioral intervention research. First, since researcher allegiance to intervention is a strong predictor of differences between two interventions that are directly compared, accounting for up to 10% of the variability in treatment outcomes (Gaffan, Tsaousis, & Kemp-Wheeler, 1995
; Luborsky, Diguer, Luborsky, & Schmidt, 1999
; Wampold, 2001
) and up to 69% of the differences between interventions (Imel, Wampold, Miller, & Fleming, 2008
; Luborsky et al., 1999
), researchers have recommended balancing allegiance when two psychological interventions are directly compared (Hollon, 1999
). Second, active and control interventions should be structurally equivalent. Structural variables include number and duration of sessions, therapist training and qualifications, format of the therapy (e.g., group or individual), and the ability of participants to discuss their particular problems. If interventions are unequal in these ways, differences between interventions may be a result of structural non-equivalencies rather than the mechanism of interest. Indeed, when structural differences between interventions and active controls are eliminated, differential efficacy may disappear. In a meta-analysis of 21 psychotherapy studies, the effect of treatment was Cohen’s d
= .47 when the control was not equivalently structured and only d
= .15 when it was (Baskin, Tierney, Minami, & Wampold, 2003
). Finally, the active control should include all non-specific factors present in MBSR. As noted above (e.g., Mohr et al. 2003), many active controls that are designed to control for non-specific factors do not contain an accepted rationale or corresponding specific ingredients and would not plausibly be offered as efficacious by providers (Wampold et al., 2010
). A well designed control should include: (a) positive expectation for intervention success by both the therapist and client (Mohr et al., 2009
), (b) a therapeutic relationship, (c) provision of a plausible alternative and adaptive explanation for distress (i.e., therapeutic rationale), and (d) some corresponding action for its alleviation (i.e., specific ingredients; Frank & Frank, 1993
The objective of the current study was to isolate mindfulness as a specific ingredient by designing a control condition that meets the criteria above, while not containing any mindfulness training. The Health Enhancement Program (HEP; MacCoon et al., 2011
) was designed to accomplish these goals. Instructors were chosen for their expertise in, and allegiance to, the class content and the mechanisms associated with its efficacy: MBSR instructors were experts in mindfulness and HEP instructors were experts in their areas (see Supplementary Materials
). Our laboratory’s interest in mindfulness is well-known. To help reduce the potential impact of this researcher allegiance, (a) researchers were not part of teaching the classes, (b) instructors played a major role in the design and implementation of their intervention (as previously discussed), and (c) one member of the design team (Z.I.), who played an important role in consultation regarding the rigor of HEP as an active control condition, has primary allegiance to common factor approaches to therapy and little allegiance to mindfulness (for a more detailed discussion, see Supplementary Materials
Both HEP and MBSR were structurally equivalent, having a group format, meeting once a week for 2.5 hours (3 hours for first and last sessions) for 8 weeks with an “all day” component (9 a.m. to 4 p.m.) after week 6, and completing the same amount of home practice (45 minutes, 6 of 7 days each week).
HEP content met the following criteria: (1) class activities were chosen to match MBSR activities as closely as possible (see ), (2) these activities represented valid, active, therapeutic ingredients in their own right, and (3) these ingredients did not include mindfulness. Thus, the purpose of walking in MBSR is to cultivate awareness in movement, whereas the purpose of walking in HEP is the cardiovascular benefits of the physical activity for cardiovascular training and followed recommendations from the Centers for Disease Control regarding intensity and frequency of physical activity (Haskell et al., 2007
). Similarly, the purpose of yoga in MBSR is largely to cultivate nonjudgmental awareness of physical sensations and respecting one’s own physical limits as they change over time. In contrast, the purpose of the balance, posture, and agility exercises in HEP’s functional movement is to augment one's physical strength, balance, agility and joint mobility resulting in a physically more resilient individual less prone to sustain injury from spontaneous or unpredictable events (e.g., tripping on a curb, slipping on icy ground, lifting a heavy object; e.g., Hu & Woollacott, 1994
; McGuine & Keene, 2006
). The music therapy component included an exercise that matched the body scan in several ways with a primary difference being the importance of the music as the change agent rather than MBSR’s emphasis on awareness of one’s own internal states. The nutrition component included didactic material and reading, both modalities used in MBSR but the content was not related to mindfulness.
Intervention content comparison.
The rationale for MBSR and HEP reflect these different active ingredients. The following is a summary of the rationale underlying MBSR: Meditative awareness is fundamental to working with problems we may have because recognizing habit patterns of mind, their impact on situations and on the body, and learning to ‘respond’ rather than simply falling into habit patterns is essential in learning skillful means of recognizing ‘problems’ and being open to more healthy options. Scientific evidence has found that mindfulness is helpful for improving various aspects of well-being, including depression, anxiety, and sleep quality.
The following is a summary of the rationale underlying HEP: In four areas, we will help you develop new habits and reinforce new ones that are known to increase well-being: (1) Physical activity enhances one’s sense of well-being, increases energy, and reduces health risks, including coronary heart disease, stroke, colon cancer and diabetes; (2) Functional movement improves posture/core strength, balance, agility and joint mobility, resulting in a physically more resilient individual less prone to sustain injury from spontaneous or unpredictable events; (3) Supportive Music and Imagery and other elements of music therapy generate positive emotions to facilitate performance on concrete tasks and is used in a group setting to create a common experience, thereby increasing relaxation-related melatonin levels (Kumar et al., 1999
), enhancing immune response (Bittman et al., 2001
; Wachi et al., 2007
), favorably changing stress-related gene expression (Bittman et al., 2005
), increasing positive mood and reducing burn out (Bittman et al., 2004
); (4) Incorporating evidence-based nutrition into one’s eating lifestyle will help reduce the risk of cardiovascular disease, hypertension, dyslipidemia, type 2 diabetes, overweight and obesity, osteoporosis, constipation, diverticular disease, iron deficiency anemia, oral disease, malnutrition, and some cancers (U.S. Department of Health and Human Services and U.S. Department of Agriculture, 2005
Thus, while HEP includes specific active ingredients meant to enhance health and well-being and thus represents an active intervention, it is also suitable as an active control for MBSR because it was matched to MBSR on non-specific elements but designed without mindfulness as one of those specific ingredients.
An additional limitation of many tests of mindfulness-based interventions is the reliance on self-report questionnaires to confirm the presence of mindfulness itself as an ingredient in training (e.g., Cohen-Katz et al., 2005
). Due to the demand characteristics inherent in this approach, the relative transparency of the items on such measures, and the often-present requirement to judge internal mental processes (Haeffel & Howard, 2010
; Nisbett & Wilson, 1977
), we used a thermal pain task to test that mindfulness was present in MBSR but not HEP. Relative to more traditional self-report mindfulness questionnaires, this task reduces the requirement to judge internal processes, equalizes to a greater degree demand characteristics across both HEP and MBSR interventions, and has instructions equally transparent to both interventions.
To validate HEP as a suitable active control for MBSR, we tested the following primary hypotheses: (1) that pain reactivity would be moderated by mindfulness but not control-related instructions for participants of MBSR but not participants of HEP; (2) that MBSR participants would show decreased pain ratings over time relative to HEP participants in the relevant instruction condition, a prediction based on evidence for the analgesic effects of mindfulness (e.g., Brown & Jones, 2010
; Grossman et al., 2007
; J. Kabat-Zinn, 1982
; Perlman, Salomons, Davidson, & Lutz, 2010
); (3) that both interventions would show reduced participant-reported mental and physical health symptoms over time, with MBSR showing greater reductions than HEP; and (4) that these predicted effects would be moderated by home practice. Similar but exploratory predictions existed for measures ranging from stress to well-being and correlations between pain data and primary self-report and practice variables (see Supplementary Materials