Mindfulness meditation has long been claimed to provide many benefits, especially stress reduction, general health, and mental functioning. These benefits are supported by quite a bit of suggestive research, but as far as I know there is little understanding of the neural mechanisms that might underlie these effects. Also, there are any number of similar behaviors (various kinds of relaxation or medication, for example), which might or might not achieve the same results, so any effects specific to one technique or another remain an open question.
David J. Creswell and colleagues have published a new study that suggests specific changes in brain functions that can be induced by “mindfulness meditation”. Furthermore, in their study, meditation produced unique effects, while other relaxation did not.
As in any brain studies, we have to retain a grain of skepticism about our weak understanding of what is going on. Creswell et al. present a plausible story about hypothesized functions of brain regions, in which the posterior cingulate cortex is “a key hub in the default mode network” and the dorsolateral prefrontal cortex and dorsal ACC are “regions considered to be important in top down executive control”. Increased “connectivity” between these regions via the “hub” “may be important for emotion regulation and stress resilience effects”. The article musters the (as yet indirect) evidence for this picture.
The point of the study is to directly test whether mindfulness meditation or other techniques measurably change this connectivity. If so, then this could be an explanatory link between the techniques and the reported psychological and physiological benefits, i.e., they work by manipulating these large scale functions of the brain, which, in turn cause the observed benefits.
The study was carefully designed to measure the functional connectivity and effects (via MRI, blood assay, and questionnaire) before and after a three day treatment. The participants were from a pool of unemployed job seekers, experiencing significant stress. Half the participants did mindful meditation, and half did a stress relief relaxation retreat. The two treatments were designed to be similar except for the “mindfulness” training.
The results were inconclusive, but suggestive. While most measures showed little or no statistical effect, one measure did show a difference between the mindful and placebo condition.
The authors conclude that “[t]hese findings suggest that a process-oriented focus on the self during meditation may shift intra-network DMN rsFC toward inter-network connectivity, coupling DMN with regions in the executive control network.” Furthermore, there is an unexplained longer term effect, “these alterations in DMN-EC rsFC can be maintained in the weeks following brief, intensive mindfulness meditation training.”
In the end, the authors “speculate that mindfulness meditation training coupled the brain’s DMN with regulatory areas of prefrontal cortex (dlPFC), which facilitated more effective emotion regulation and stress resilience”.
This is a well designed study, but it is difficult to draw strong conclusions. Despite the careful methodology, there are many questions about these results. From this tiny sample (N = 35), the statistical measures have little power, so we cannot be surprised that many of the results were too small to consider significant.
I note that the working hypotheses are based on a relative handful of studies, and describe brain functions at a rather coarse level. The long and the short of it is that we have “suggestions” that these areas are related to behavior and physiology, but not much understanding of how this might work. It isn’t surprising, then, that poorly understood behavioral intervention has a rather hazy effect on poorly understood neural systems.
Even taking the results at face value, we can wonder about the three day intervention. Would shorter or longer training have proportional effects? (Notably, none of the participants continued the training at home.) What details of the training really cause the effects? What, exactly, is “mindfulness” in the brain?
Overall, this is a well designed study, and the results are suggestive. But they are scarcely definitive. Clearly, it will be interesting to see results from additional studies in the future.
- Creswell, J. David, Adrienne A. Taren, Emily K. Lindsay, Carol M. Greco, Peter J. Gianaros, April Fairgrieve, Anna L. Marsland, Kirk Warren Brown, Baldwin M. Way, Rhonda K. Rosen, and Jennifer L. Ferris, Alterations in resting state functional connectivity link mindfulness meditation with reduced interleukin-6: a randomized controlled trial. Biological Psychiatry, http://www.sciencedirect.com/science/article/pii/S0006322316000792