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Can meditation restructure our brains? Several recent studies have claimed that, with daily practice, meditation can boost grey matter volume and density in some brain areas in just eight short weeks. But a study published today (May 20) in Science Advances—one with the largest sample size yet—was not able to replicate these findings. 

“There was frankly a lot of hype . . . saying that if you meditated for eight weeks you could change the volume of your prefrontal cortex. That is false,” study coauthor Richard Davidson, a neuroscientist at the University of Wisconsin-Madison, tells The Scientist. He adds that beneficial functional and behavioral changes due to meditation are likely to occur much faster, however. 

“From a methodological standpoint, [the study] really addressed some of the concerns that are common in a lot of imaging research,” says Matthew Jerram, a psychology researcher at Suffolk University in Boston who was not involved in the study. “I think a lot of the people who’ve done research on . . . mindfulness based treatments will probably be disappointed. . . . But if they’re really honest with each other, I don’t think they’ll be surprised.” 

Amishi Jha, a psychologist at the University of Miami who also was not involved in the work, agrees that the study “astutely addressed” flaws of the studies it replicated. “This is a stellar study,” she writes in an email to The Scientist.

Based on their own and other groups’ previous studies on long-term meditators, the study’s authors say that meditation can eventually boost brain volume and neuron density in some key areas—but, they add, it’s likely these changes take much longer than eight weeks to occur.

Investigating meditation’s effects on the brain

The study focused on a meditation program called Mindfulness Based Stress Reduction (MBSR), a popular mindfulness intervention that clinicians developed to help patients cope with pain. The authors and other experts are quick to point out that MBSR is very effective—studies have found that it helps reduce stress and lessen symptoms of anxiety, depression, and chronic pain. 

Previous studies have reported that MBSR, which involves 24-30 hours of meditation practice over two months, led to an increase in gray matter density—a measure of the amount of cortical grey matter in a given area — and gray matter volume—the total size of the grey matter— in several brain areas including the hippocampus, posterior cingulate cortex, and the temporoparietal junction. These regions are involved in learning and memory and emotional regulation, and the study authors interpreted the findings as evidence that meditation might, in a short time span, improve both. 

But those same studies also used small sample sizes, typically one to two dozen participants. And many didn’t use controls that also received positive interventions, instead of looking at the effect of a treatment on individuals versus a lack of intervention. Thus, in previous studies, the fact that there was a positive intervention at all may have caused a change, rather than meditation specifically. The authors and experts tell The Scientist that to be certain that MBSR was responsible for neurological changes, researchers needed to compare its effects to other positive interventions, such as those focused on diet and exercise. 

So over seven years, researchers at the University of Wisconsin-Madison conducted two randomized controlled trials with more than 70 subjects each in the experimental and control groups. In both, patients were placed in one of three groups: a group that attended an MBSR session each week and practiced mindfulness-based relaxation techniques daily, a control group that received a different positive wellbeing intervention training called HEP—which focuses on music therapy, healthy eating, and exercise—and a third group that was told they would get one of these interventions later. The patients received structural MRI brain scans before and after eight weeks of these interventions (or in the control group’s case, eight weeks of waiting). 

Drawing a blank

I think a lot of the people who’ve done research on . . . mindfulness based treatments will probably be disappointed. . . . But if they’re really honest with each other, I don’t think they’ll be surprised.

—Matthew Jerram, University of Suffolk

Davidson says that based on previous studies, he expected MBSR to lead to structural changes within the brain. The researchers compared gray matter density, gray matter volume, and cortical thickness before and after the intervention in various regions of interest, including the hippocampus, the posterior cingulate cortex, and the temporoparietal junction. The team chose regions other researchers had found to have MBSR-linked changes in size or density, plus other regions that are involved in emotional processing. But in the brain regions they analyzed, the researchers didn’t find any differences when comparing changes in gray matter density, gray matter volume, or cortical thickness among the groups. The researchers also found no differences among the groups when they looked at changes in volume and density across the whole brain over the course of the experiment.   

Within the MBSR group, the researchers did find that people who practiced the mindfulness meditation-based techniques they’d learned in the course for more than 22 minutes each day had significantly smaller amygdalas—a region associated with stress and fear—after eight weeks. 

Davidson says that this connection is to be expected. Brain structure changes occur when people practice other skills, like exercise or learning a new instrument, so it’s likely that changes also come about when practicing meditation—eventually. “It’s not just 24 or 30 hours of practice, it’s going to take more. And it’s kind of not surprising, because in order to develop a skill, we need thousands of hours of practice, not 25 hours of practice,” says Davidson.

The contrast between the results of earlier studies with fewer subjects and the current work aligns with a study earlier this year that found small sample sizes in MRI-based research can generate misleading results, and that data drawn from typical study sample sizes is insufficient to be reliable. 

Davidson says he hopes that the new meditation study will serve as a “useful corrective in the field and help to tone down some of the hype that has been associated with these kinds of practices.” 

“We’re big fans of meditation,” he says, “but we’re big fans of truth, too.”