Review articleCognitive effects of MBSR/MBCT: A systematic review of neuropsychological outcomes
Introduction
Mindfulness has grown exponentially in the last 15 years as a topic of scientific research and clinical practise. Research has found mindfulness to be associated with many health and well-being indicators. Health benefits include decreased levels of stress and anxiety, improved emotional, mental and physiological regulation and promotion of brain plasticity (Arch and Craske, 2006, Grossman et al., 2004, Hoge et al., 2012, Holzel et al., 2011, Keng et al., 2011, Mankus et al., 2013, Marchand, 2012). As such, interest in mindfulness is beginning to spread beyond clinical settings into education, sports and businesses. As more and more people practise mindfulness, it becomes important to better understand how mindfulness actually works.
Jon Kabat-Zinn, the founder of Mindfulness Based Stress Reduction (MBSR), defines mindfulness as “the awareness that emerges through paying attention on purpose, in the present moment, and nonjudgmentally to the unfolding of experience moment by moment” (2003). An operational definition proposes that mindfulness is comprised of the two components: attention regulation and orientation to experience characterised by an open and non-judgemental attitude (Bishop et al., 2004). Meditation is the method most commonly used to train mindfulness. Lutz, Slagter, Dunne, and Davidson (2008) propose that meditation styles or meditation traditions can be categorised as either focused meditation (FM) or open monitoring (OM) but see Nash and Newberg (2013) for an alternative categorisation. FM involves using an object as a focal point for attention and returning attention back to the object when the mind wanders away. This type of training is thought to be correlated with improvements in sustained (concentration) and selective attention assessable by performance on neuropsychological tests such as the attentional network task (ANT, Fan, McCandliss, Sommer, Raz, & Posner, 2002) and the continuous performance task (CPT, Shalev, Ben-Simon, Mevorach, Cohen, & Tsal, 2011). OM does not have an explicit object of focus, instead it involves noticing all experiences that arise. This type of meditation is thought to train a non-reactive awareness and develop an awareness of automatic emotional and thought processes. Commonly, FM is introduced before OM, as OM is considered more difficult without first stabilising attention through FM practise (Wallace, 2006).
The aim of this paper was to examine the evidence for cognitive effects from mindfulness training, specifically the effects promoted through clinical mindfulness programs such as MBCT and MBSR. If mindfulness exerts its salutary effects through cognitive processes, such as attention and awareness, then studies investigating this relationship are crucial to understanding how mindfulness works. Knowing how mindfulness works will enable clinicians to confidently select, adapt and modify treatment programs to different patient groups. Additionally, mindfulness has been predominantly assessed by self-report measures. Concerns have been raised regarding the validity of subjective measures of this psychological construct (Belzer et al., 2013, Grossman, 2011). Establishing cognitive correlates of mindfulness may offer an objective performance-based measure of mindfulness – an area identified as important for the future development of mindfulness in research and science (Garland and Gaylord, 2009, Sauer et al., 2013).
A previous review which investigated whether mindfulness training improved cognitive abilities found that mindfulness did significantly improve the attentional sub-processes of selective, sustained and executive attention (Chiesa, Calati, & Serretti, 2011). Working memory capacity and some executive functions, such as verbal fluency and inhibition of pre-potent responses, were also shown to be enhanced. Furthermore, particular cognitive changes were associated with the type of meditation engaged. For example, FM promoted selective and executive attention while OM developed sustained attention, however, sustained attention was previously thought to be an effect of FM (Bishop et al.). Chiesa et al.’s review covered different forms of meditation, ranging from mantra and visualisation to Buddhist based Zen, Shamatha-Vipassana and secularised forms such as ACT, MBCT and MBSR. Programs also varied in duration and intensity from a brief 20 min induction (Wenk-Sormaz, 2005) to 3-month intensive meditation retreats requiring 10–12 h of daily practise (Slagter et al., 2007). There are marked differences in conceptualisation, goals, and techniques taught within different meditation styles and both meditation style and amount of experience are likely associated with different cognitive outcomes (Chiesa & Malinowski, 2011). Thus, comparisons of cognitive outcomes from mindfulness training ought to be conducted on standardised forms of mindfulness. MBSR and MBCT are both standardised and manualised forms of mindfulness intervention. A review of the available literature on such standardised interventions may be useful.
MBSR is the prototypical mindfulness intervention originally conceived for treatment of stress and anxiety (Kabat-Zinn et al., 1985, Kabat-Zinn et al., 1992). MBCT was modelled after MBSR and combines cognitive behavioural therapy (CBT) with mindfulness for the treatment of recurrent depression (Teasdale, Segal, & Williams, 1995). Both are 8-week group programs designed to teach mindfulness skills through formal sitting meditation and other mindfulness exercises. It is assumed that mindfulness skills help the patient to become aware of their habitual cognitive patterns and exit those that perpetuate negative symptoms. However, MBSR/MBCT differs from CBT; the focus of mindfulness is not to change thought content but to become aware of the thought process itself. MBSR/MBCT differs from other psychotherapies such as ACT and DBT, where mindfulness is not a core skill and formal meditation is not taught. MBSR/MBCT also differs from Buddhist based practices in its clinical orientation and secular nature.
Since Chiesa et al. (2011) included many other mindfulness protocols along with some MBSR and MBCT studies, it is not clear what cognitive effects were specific to MBSR/MBCT treatment. In this review we selected prospective studies where MBSR/MBCT intervention was delivered and outcomes of treatment were measured post-intervention. Some studies overlapped with those in Chiesa et al.’s review but a significant number were new studies. We hope this approach reveals more consistent findings than Chiesa et al.’s review and elucidate what cognitive effects result from MBCT/MBSR treatment. We chose MBSR/MBCT interventions because the mindfulness training is standardised within these programs. Furthermore, these interventions are growing in popularity and are an ecological representation of how people are likely to experience mindfulness within a clinical setting.
The cognitive processes examined in mindfulness research include attention, executive functions and memory. We briefly describe theorised models for these processes to provide a framework from which to interpret findings. However, the following outline of visual attention, executive function and working memory are hypothesised subprocesses and should not be taken as reflective of conceptual or neural underpinnings. The visual attentional system is thought to be comprised of the subsystems: (1) alerting, (2) orienting and (3) executive attention (Posner & Petersen, 1990). Alerting refers to a basic awakeness or arousal to stimuli, and orienting (also referred to as selective attention) functions to prioritise target events by selecting from the array of incoming sensory information. The role of executive attention is goal monitoring, conflict detection and resolution. The Attentional Network Test (ANT, Fan et al., 2002) was designed to assess all three subcomponents. Executive attention itself is subserved by three subsystems of the executive network which include (1) mental set shifting; (2) updating and monitoring; and (3) inhibition (Miyake et al., 2000). The subsystems of the executive network handle higher order cognitive processes involved in activities such as planning, prioritising and problem solving. Mental set shifting involves switching from one task set to another, while updating requires monitoring of incoming information and updating old, no longer relevant, information held in working memory with newer information relevant to the current task. Inhibition is described as the ability to deliberately inhibit prepotent automatic responses, of which the Stroop colour-word task is a prototypical measure (Stroop, 1935). We only further discuss working memory because it is most closely aligned with mindfulness. Mindfulness requires the regulation of attention toward present moment experiences, working memory is responsible for storage of information that is relevant to the immediate experience and is also closely connected with attention and awareness. Working memory is thought to be comprised of an auditory and a visual/spatial store governed by an executive control allocating attention (Baddeley & Hitch, 1974). Baddeley (1992) has claimed that consciousness or awareness operates through working memory while others have argued that working memory depends upon awareness (Baars, 1997, Crick and Koch, 1990), either way the relationship is an intimate one. Complex span tasks are used to measure working memory capacity. Simple span tasks require a straightforward recall of items presented, while complex span tasks require not only the recall of items, but also involve conducting another task designed to interfere with the process of storage. Thus, working memory measures not only the ability to store, but also the ability to resist distraction, which is a central tenet of mindfulness.
While the above frameworks treat processes of attention, working memory and executive function as unitary it is apparent from the brief descriptions that processes do overlap and interact within a dynamic cognitive system. Executive functions support attention and working memory while working memory also draws upon attention. These classifications of cognitive subsystems are heuristic and interpretation of outcomes should be considered in light of this.
Section snippets
Eligibility criteria
Controlled experimental studies were of adult populations (18 and above) delivering MBCT/MBSR intervention (or equivalent), which have at least one outcome measure that is an objective neuropsychological measure of cognition. The studies were drawn from English language peer reviewed journal articles published between January 2000 and February 2015. Mindfulness research only began to grow exponentially in early 2000. A search of a popular database (Scopus) using the search terms “mindfulness”
Search results
An initial search of databases resulted in 10,962 articles. Screening at title and abstract level and removal of duplicates resulted in the exclusion of 10,891 articles. This left 71 for full text screening, which further excluded 53, mainly due to studies not employing a MBSR or MBCT intervention or equivalent (18) or were cross-sectional studies (11). Refer to Fig. 1 for full list of reasons for excluded studies. Following, a total of 18 studies were included in this systematic review.
Study characteristics
Studies
Discussion
The review set out to examine what cognitive abilities would be improved following standardised mindfulness interventions MBSR and MBCT. Contrary to theoretical expectations that mindfulness training would improve sustained, selective and executive attention, we found no evidence for this. Similarly, there was limited evidence for improvements in executive functions. However, there was preliminary evidence for working memory capacity and autobiographical memory improvements as well as affects
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