Meditation—Still Many Unknowns


by Jim Schnabel

March 11, 2011

“Practicing meditation changes your brain” is a common headline in popular-media accounts of meditation research. But brain changes occur with any practiced task. The real question is, how does meditation change your brain? And are those changes always good ones?

Despite years of research and hundreds of studies, these scientific questions are still largely unsettled, in part because there are unique challenges to researchers in this field—including the difficulty of doing placebo-type controls, and the variety of techniques that fall under the term “meditation.”

“It’s still a very young field,” says Antoine Lutz, a researcher at the largest academic laboratory for meditation research, the Waisman Laboratory for Brain Imaging and Behavior, headed by Richard Davidson at the University of Wisconsin–Madison.

Reported effects

The behavioral differences that seem to be most commonly reported in studies of new or long-time meditators include an increase in the ability to focus one’s attention, an increase in the ability to regulate one’s emotions, a decrease in stress and pain, and cognitive changes that include an enhanced sense of empathy and “connectedness.”

What causes these effects? Researchers hypothesize a complex set of brain activities, in which the “mind” becomes more aware of thoughts and feelings yet at the same time is less affected by them. “We learn to bring a space between the emotion and the reaction,” says Britta Hölzel, a researcher at Massachussetts General Hospital and Harvard Medical School, and lead author of one of the first “clinical trial” type brain imaging studies of meditators.

The study, which appeared Jan. 30 in Psychiatry Research: Neuroimaging, examined a popular meditation technique known as Mindfulness-Based Stress Reduction (MBSR). Sixteen people with no prior experience of meditation took an eight-week MBSR course and—on average—showed significant increases in their “mindfulness” skills on three out of five tests. Magnetic resonance imaging (MRI) scans also showed a slightly larger volume in three brain regions: the hippocampus, the posterior cingulate cortex, and the temporo-parietal junction. By contrast, a control group of 17 people on the waiting list for the MBSR course showed no such changes.

“We don’t have a clear understanding neurologically what is really happening,” Hölzel says. But this study, as well as prior studies, hint that mindfulness meditation can boost brain regions involved in imaginatively “stepping back” and observing oneself. “The posterior cingulate cortex, the temporoparietal junction, and the hippocampus all form a network that gets involved when we imagine ourselves from different perspectives,” she adds.

Many styles

Like other imaging studies of meditators, this one enrolled a relatively small number of subjects, and thus lacked the statistical power to generate strong evidence:  “The interpretations are pretty limited at this point,” Hölzel says. “We have to do more studies, and we need replication.”

Replication has been somewhat elusive in this part of the field. Most structural imaging studies have compared the brains of long-term meditators and non-meditators, and their findings about brain differences have had little overlap.

One reason for this failure to converge—aside from the small numbers of subjects—is that these studies have not all focused on the same meditation style. As Lutz and colleagues noted in a 2008 review paper, mindfulness-based techniques represent just one of many sets of meditation practices, each presumably having its own distinct impact on the brain. Lutz says that “even the term mindfulness as it is used in therapeutic settings covers many sub-techniques.”

Dosing and controlling

A further hurdle that the field has yet to overcome concerns the “dose response” to meditation—in other words, how its effects on the brain differ with increasing practice. In a functional MRI study reported in 2007, a group including Lutz and other members of the Davidson lab found that certain attention-related brain regions used to maintain the meditative state were more active in practiced meditators compared with non-meditators—yet those same regions were less active in very highly practiced meditators, as if extended practice had made them less necessary. “We have very little understanding so far about the dose response to meditation, and I think that’s a tremendous challenge,” says Lutz.

Perhaps the greatest challenge facing the field has been that of defining a true “control group.” When testing pharmaceuticals, researchers can control for potentially confounding factors by randomly assigning people to two groups, then giving one the real treatment, and the other a lookalike sham treatment or “placebo”—so that the only difference in their experience is the ingredient being tested. But researchers have never achieved this level of control in meditation research.

For example, in the recent study by Hölzel and colleagues, the control group were non-meditators on the MBSR course waiting list. Their experience during the study would have differed from the course-takers’ in a number of ways, possibly including less physical exercise—and physical exercise is known to be able to stimulate neural stem cells in the hippocampus and boost its volume. “Any kind of intervention may have an impact on someone, and unless we have proper controls we can’t know what parts of the intervention account for that impact,” says Lutz.

Both Lutz and Hölzel say that they and their colleagues are now designing studies with “active control groups” whose experience will include the expectation of therapeutic benefits as well as every other part of the mindfulness meditation course—“only without the mindfulness ingredient,” says Lutz.

What about side effects?

Meditation techniques have been practiced for so long that they are widely assumed to be safe. Yet anecdotal reports from meditation teachers, as well as reports in medical journals, make clear that meditation occasionally triggers unpleasant experiences, and even conditions requiring psychiatric care. “There are certain alterations of consciousness with meditation that are expected and desireable, yet sometimes those altered states can provoke a frank psychotic episode,” says Willoughby Britton, a researcher at Brown University who recently began looking into such reports.

Meditation-induced psychoses include a delusional condition, sometimes termed the “qi gong psychotic reaction” for its prevalence among adherents of a popular Chinese meditation style. A recent report in a medical journal described a Chinese-American qi gong practitioner who drove her car into a wall, because she “believed that she was invincible and wanted to test her superpowers in the crash.”

A related type of reaction known to be experienced by some meditators is “depersonalization,” in which a person’s conscious mind seems to disconnect from the rest of her brain, so that she observes her thoughts and actions going on beyond her control. Although some people find the experience unexpected and unpleasant enough to get medical help, Britton emphasizes that it is to some extent what meditation is meant to do:  “With depersonalization people can feel that they’re disconnected from their emotions,” she says. “Yet that’s a very common goal of meditators: to have emotions and not be identified with them.”

Britton’s chief interest now is to understand the risk factors for these adverse experiences. A history of trauma is one that meditation teachers frequently mention, she says, although sometimes there is no history to suggest an added risk. “The people I’ve interviewed who have been hospitalized don’t seem to have any trauma history, psychiatric history, or even family psychiatric history,” Britton says.

One risk factor already noted in the literature is simply the dose of meditation, which for some dedicated meditators exceeds several hours per day. “It’s wrong to think that you can do meditation all the time and there’s no overdosing on it,” says Britton. “It’s often marketed as a mere relaxation technique, but that’s just false advertising.”