Research on the eff ects of MBSR continues to grow rapidly, especially following the call by Bishop (2002) for greater conceptual and empirical development to supplant observational studies conducted during the early years of MBSR. Reviews of MBSR outcome studies include those by Salmon et al. (2004), meta-analyses by Baer (2003), Grossman, Niemann, Schmidt, and Walach (2004), Chiesa and Serretti (2009), Ledesma and Kumano (2009), and a theoretical and empirical review by Brown, Ryan, and Creswell (2007). Studies in these reviews were based on a wide range of target populations, including health care professionals, inner-city populations, prison populations, medical patients, psychiatric patients, and anxious patients, with males and non-whites somewhat underrepresented.
Earlier studies focused on MBSR in its original context as a stress management program for various medical conditions, notable exceptions being studies by Kabat-Zinn and col- leagues (1992), targeting anxiety and panic disorder, and Teasdale, Moore, Hayhurst, Pope, Williams, and Segal (2001), focusing on depression relapse. Overall, moderate eff ect sizes for MBSR on stress and related mental health measures were consistently reported: d=.54 (Grossman et al., 2004), d=.59 (Baer, 2003), and d=.48 (Ledesma & Kumano, 2009).
Th e consensus of these reviews is that MBSR shows promise as a clinical interven- tion, but more rigorous research methodology incorporating randomized control trials, larger sample sizes, long-term follow-up, and comparisons with other interventions is needed. Regarding the latter, randomized trials to date have employed primarily no- treatment, usual-treatment, or wait-list control groups. As a result, these studies are limited in their ability to account for primary MBSR eff ects due to lack of control for nonspecifi c factors (Baer, 2003; Chiesa & Serretti, 2009; Grossman et al., 2004). Given the distinctive “clinic within a course” format of MBSR, it is understandable why there are few suitable alternative interventions with which to compare it. However, Chiesa and Serretti (2009) did report one cohort-control study in which an MBSR course for mental health caregivers had a highly signifi cant and benefi cial eff ect on stress and well-being, compared to a didactic control condition matched for time commitment, instructor contact, and group delivery modality (Shapiro, Brown, & Biegel, 2007).
Th e broad range of medical and health conditions for which MBSR has been found to be helpful has led to debate as to the nature of its impact, which is clearly not disease-specifi c. Th is is clear enough, given that clinically (as opposed to research)
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based MBSR program groups are heterogeneous in composition. In fact, heterogeneity is a fundamental element of the program as originally conceived. Th e intended purpose is to emphasize the breadth of human suff ering and resourcefulness of program par- ticipants, who are drawn from all walks of life, including medical patients and hospital personnel. Whatever the eff ect of participant heterogeneity on program outcome may be, it has not been evaluated in research to date, which has focused on MBSR for spe- cifi c populations. Rapidly advancing research has produced strong evidence of MBSR benefi ts for diverse patient groups (Grossman et al., 2004), including chronic pain (Pradhan et al., 2007; Morone, Greco, and Weiner, 2008), and recurrent depression (Kuyken, et al., 2008).
Th us far, MBSR has yet to be the focus of deconstruction research, evaluating the relative contribution of program elements to the overall impact of the program as a whole. However, two key elements of MBSR—meditation and Yoga—have a long history of research-based application in the stress reduction literature (Benson, 1975; Lehrer & Carrington, 2002;
Khalsa, 2004). It is noteworthy that the most recent revision of an authoritative, empirically based guide to clinical stress management now includes a section on Eastern meditation and therapeutic disciplines (Lerhrer, Woolfolk, & Sime, 2007).
Th e generally favorable convergence of MBSR research fi ndings across a wide range of medical and related psychological conditions is certainly noteworthy, but at this junc- ture, as with any multicomponent intervention, it is diffi cult to determine what specifi c elements account for the program’s eff ectiveness. In the hands of skilled practitioners, MBSR incorporates a range of benefi cial factors common to most forms of psychother- apy (Hubble, Duncan, & Miller, 1999), including: (a) expectancy factors, (b) patient/
extratherapeutic factors, (c) positive relationship factors, and (d) specifi c techniques. Al- though we stated earlier that MBSR is not, strictly speaking, a form of psychotherapy, it is certainly true that experienced instructors are psychologically sophisticated and bring a high level of expertise and sensitivity to their work. In this regard, one could make a fairly convincing case that MBSR shares features with psychotherapy that have proven eff ective in treating a wide range of symptoms of distress. As noted, individual studies assessing the impact of MBSR on anxiety and panic (Kabat-Zinn, 1992), as well as de- pression relapse (Teasdale, et al., 2001) attest to its fl exibility in addressing psychological distress across diff erent diagnostic categories.
Another perspective is to consider common aspects of psychopathology and then de- termine the degree to which they are addressed in MBSR intervention elements. Harvey, Watkins, Mansell, and Shafran (2004) provide a useful framework in this regard, referred to as a “transdiagnostic approach” to cognitive behavioral interventions. Th e foundation of the transdiagnostic model rests on evidence of high rates of co-morbidity across psy- chological diagnostic categories, and the comparative rarity of “pure” unitary diagnoses, which collectively suggest common underlying mechanisms across disorders. Of the fi ve hypothesized common processes discussed by Harvey et al. (2004), attention is clearly the most relevant for MBSR, in terms of both self-focused and selective aspects. Baer (2007) notes that the widespread eff ects of mindfulness enhancing interventions may in part be
due to their impact on attention control problems evident in a broad range of clinical conditions.
However, as Harvey et al. (2004) note, although attention is a key aspect of mind- fulness and shows considerable promise as an outcome variable, empirical research is at only a very early stage. Attention is one of three key variables in the conceptual model of mindfulness (along with attitude and intention) proposed by Shapiro, Carlson, Astin, and Freedman (2006), who further subdivide it into several components amenable to empirical investigation. Th ese include sustained attention (vigilance), being able to shift attention from one focal point to another, and the capacity to limit cognitive elaborations that tend to blossom once the seed of attention is focused (or “planted”) on a specifi c object of awareness. Posner and Peterson (1990) underscore the adaptive signifi cance of attention by noting the existence of both dedicated and network ana- tomical loci mediating specifi c functions amenable to experimental research. Th is work- ing model has stimulated subsequent neurocognitive research on attentional networks with increasing clinical relevance (Raz & Buhle, 2006). A study by Jha, Krompinger, and Baime (2007) compared participants in two mindfulness programs with a non- meditation control group on laboratory measures of alerting, orienting, and confl ict monitoring (task prioritizing) attention components. Participants in one group had no prior meditation experience and received the standard eight-week MBSR training program. Th ose in the second group were experienced meditators who participated in a one-month intensive mindfulness retreat. Control subjects neither had meditation experience nor received any training during the study. Retreat participants, adept at confl ict monitoring to begin with, showed improved performance in alerting, compared to controls and MBSR participants. And the standard MBSR group enhanced both orienting and confl ict monitoring performance.
With respect to MBSR as an intervention for diagnostically-specifi c clinical condi- tions, such as stress, anxiety, or depression, research is needed to establish its effi cacy compared to other treatment modalities. According to a recent review by Lehrer and Woolfolk (2007), MBSR has yet to be compared to other stress management protocols such as relaxation training, biofeedback, non-MBSR meditation, or CBT-based proto- cols. Clearly the time has come to rectify this shortcoming in the research literature. For one thing, .it is important to avoid the indiscriminate application of the program with individuals or populations for whom it is not well suited (Kocovski, Segal, & Battista, 2009), such as those with severely debilitating psychological disorders (e.g., refractory depression, suicidality, untreated psychosis, etc.). For another, the importance of devel- oping clinical “best practice” guidelines is a clear incentive to compare the effi cacy of MBSR with other interventions for specifi c clinical groups.
We end this section with mention of burgeoning research on neurobiological func- tions, which is of particular relevance for MBSR because of its focus on stress manage- ment. Drawing on a wide array of measures, Treadway and Lazar (2009) provide a useful summary of these studies, which provide evidence of four signifi cant clinical outcomes:
(a) increased “in the moment” experience, (b) enhanced positive aff ect, (c) lower stress
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reactivity, and (d) cognitive vitality. In the future, it is anticipated that mindfulness re- search will increasingly incorporate the neurobiological assessment domain, along with ubiquitous self-report measures currently utilized.