Entering medical school fresh out of Princeton, Judson Brewer found himself one of many stressed out medical students.

“I wasn’t coping well, I was frustrated and I was just getting into my way,” said Brewer. “Then, I started meditating, and that was the best thing that has happened to me.”

Twenty years later, Brewer, now the director of research at the Center of Mindfulness at the University of Massachusetts Medical School and professor of psychiatry at the Yale School of Medicine, is focused on finding out how meditation affects the human brain. In a recent paper, published this September in the Journal of Cognitive, Affective, & Behavioral Neuroscience, a team of researchers led by Brewer reports that expert meditators see reduced activity in a brain network associated with mind wandering. These findings held true for a sample size significantly larger than those of previous studies, and suggested that experienced meditators may indeed be better able to shut out distractions compared to novice ones.

“The one major contribution of this study lies in showing that previous findings are reproducible,” said Massachusetts General Hospital neuroscientist Thomas Zeffiro, acknowledging the recent upswell of concern following a study that suggested that over half of the studies published in leading psychology journals may not be reproducible.

Brewer added that while previous studies compared brain activity during meditation to brain activity during rest, this study compared the former with brain activity during another cognitive task.

Working with meditators who had an average of 10,000 hours of experience, psychiatry professor Kathleen Garrison and the team found significantly reduced activity in the default mode network, the brain network implicated in self-related thinking and mind wandering. They found an especially dramatic decrease in activity in the posterior cingulate cortex, the region of the brain involved in self-related thinking, Brewer said.

The team has not shown that meditation is responsible for these changes, Zeffiro cautioned. It is perfectly reasonable to believe that mindfulness training does lead to better focus, but it is also possible that the group of meditators is self-selecting, he said.

“It’s a chicken-and-egg issue, just like with any other learned skill,” Zeffiro said. “Do great musicians exhibit the differences in brain activity we see because of the practice it takes to become great, or do they become great thanks to differences that already existed in the first place?”

The next step, said Zeffiro, is to conduct longitudinal studies where researchers follow individuals randomly assigned to meditation or non-meditation groups across an extended period. This will not only provide stronger evidence of a causal relationship but also allow researchers to capture the time point at which changes in brain activity take place.

The research findings have generated interest among Yalies. Members of YMindful, a community of Yalies which hosts weekly meditation sessions, are hoping that such studies will draw more students to its events.

“It is nice to have affirmation that the feelings I experience [while meditating] are backed up by science,” said YMindful president Ivy Ren ’18.

Six percent of the American population meditates, according to data from the 2012 National Health Interview Survey.