The neuroscience of mindfulness meditation

| Research over the past two decades broadly supports the claim that mindfulness meditation — practiced widely for the reduction of stress and promotion of health — exerts beneficial effects on physical and mental health, and cognitive performance. Recent neuroimaging studies have begun to uncover the brain areas and networks that mediate these positive effects. However, the underlying neural mechanisms remain unclear, and it is apparent that more methodologically rigorous studies are required if we are to gain a full understanding of the neuronal and molecular bases of the changes in the brain that accompany mindfulness meditation. R E V I E W S NATURE REVIEWS | NEUROSCIENCE VOLUME 16 | APRIL 2015 | 213 © 2015 Macmillan Publishers Limited. All rights reserved Correlational studies Studies that assess the co-variation between two variables: for example, co-variation of functional or structural properties of the brain and a behavioural variable, such as reported stress. groups of non-meditators matched on various dimensions9,18. The rationale was that any effects of meditation would be most easily detectable in highly experienced practitioners. A number of cross-sectional studies revealed differences in brain structure and function associated with meditation (see below). Although these differences may constitute training-induced effects, a cross-sectional study design precludes causal attribution: it is possible that there are pre-existing differences in the brains of meditators, which might be linked to their interest in meditation, personality or temperament2,19. Although correlational studies have attempted to discover whether more meditation experience is related to larger changes in brain structure or function, such correlations still cannot prove that meditation practice has caused the changes because it is possible that individuals with these particular brain characteristics may be drawn to longer meditation practice. More recent research has used longitudinal designs, which compare data from one or more groups at several time points and ideally include a (preferably active) control condition and random assignment to conditions11–14,20–25. In meditation research, longitudinal studies are still relatively rare. Among those studies, some have investigated the effects of mindfulness training over just a few days, whereas others have investigated programmes of 1 to 3 months. Some of these studies have revealed changes in behaviour, brain structure and function11–14,20–25. A lack of similar changes in the control group suggests that meditation has caused the observed changes, especially when other potentially confounding variables are controlled for properly20–22. Novice meditators versus expert meditators. Although most cross-sectional studies included long-term meditators9,17, longitudinal studies are often conducted in beginners or naive subjects. Thus, differences in the results of cross-sectional and longitudinal analyses might be attributed to the different brain regions used during learning of meditation versus those used during the continued practice of an acquired skill. It would be interesting to follow subjects over a long-term period of practice to determine whether changes induced by meditation training persist in the absence of continued practice. However, such long-term longitudinal studies would be compromised by feasibility constraints, and it is likely that future longitudinal studies will remain restricted to relatively short training periods2. Control groups and interventions. It is important to control for variables that may be confounded with meditation training, such as changes in lifestyle and diet that might accompany the meditation practice or the expectancy and intention that meditation beginners bring to their practice. Researchers must carefully determine which variables are integral aspects of the meditation training and which can be controlled for. Some earlier studies only controlled for the length of time that the individual has practised meditation and the effects of repeated testing, Box 1 | Mindfulness meditation Different styles and forms of meditation are found in almost all cultures and religions. Mindfulness meditation originally stems from Buddhist meditation traditions. Since the 1990s, mindfulness meditation has been applied to multiple mental and physical health conditions, and has received much attention in psychological research. In current clinical and research contexts, mindfulness meditation is typically described as non-judgemental attention to experiences in the present moment. This definition encompasses the Buddhist concepts of mindfulness and equanimity and describes practices that require both the regulation of attention (in order to maintain the focus on immediate experiences, such as thoughts, emotions, body posture and sensations) and the ability to approach one’s experiences with openness and acceptance. Mindfulness meditation can be subdivided into methods involving focused attention and those involving open monitoring of present-moment experience. The mindfulness practices that have been the subject of neuroscientific research comprise a broad range of methods and techniques, including Buddhist meditation traditions, such as Vipassana meditation, Dzogchen and Zen, as well as mindfulness-based approaches such as integrative body–mind training (IBMT), mindfulness-based stress reduction (MBSR) and clinical interventions based on MBSR. Both MBSR and IBMT have adopted mindfulness practices from the Buddhist traditions and aim to develop moment-to-moment, non-judgemental awareness through various techniques. IBMT has been categorized in the literature as open-monitoring mindfulness meditation, whereas MBSR includes both focused attention and open-monitoring practices. It has been suggested that mindfulness meditation includes at least three components that interact closely to constitute a process of enhanced self-regulation: enhanced attention control, improved emotion regulation and altered self-awareness (diminished self-referential processing and enhanced body awareness) (see the figure, part a). Mindfulness meditation can be roughly divided into three different stages of practice — early, middle (intermediate) and advanced — that involve different amounts of effort (see the figure, part b). Nature Reviews | Neuroscience a b Mindfulness meditation Middle stage Advanced stage Early stage Effort to reduce mind wandering Effortless being Effortful doing Attention control Emotion regulation Selfawareness Self-regulation R E V I E W S 214 | APRIL 2015 | VOLUME 16 www.nature.com/reviews/neuro © 2015 Macmillan Publishers Limited. All rights reserved