Open any magazine (this one, for example) and you’ll find that mindfulness has gone mainstream. You’ll also notice there are studies that purport to show meditation’s benefits on just about everything, from kids’ math scores and migraine length to HIV management and bouncing back after a crisis. Now, an elaborate new forthcoming study looks at how the brains of meditators respond to pain, to be published in the Journal of Neuroscience.

Dr. Fadel Zeidan, assistant professor of neurobiology and anatomy at Wake Forest Baptist Medical Center, has studied mindfulness for 15 years and has observed improved health outcomes as a result. “But what if this is all just a placebo?” he wondered. “What if people are reporting improvements in health and reductions in pain just because of meditation’s reputation as a health-promoting practice?” He wanted to find out, so he designed a trial that included a placebo group.

Zeidan recruited 75 healthy, pain-free people and scanned their brains using an MRI while they experienced painful heat with a 120-degree thermal probe. Then, the researchers sorted them into four groups and gave them four days of training. Everyone thought they were getting the real intervention, but most of them were getting a sham treatment.

“I want to be restrained about the efficacy of mindfulness, and the way to be restrained about it is by making it harder and harder to demonstrate its effectiveness,” Zeidan says.

First, there was a placebo cream group that participants were told reduces pain over time, Zeidan says (it was really just petroleum jelly). For four days, they rubbed it on the back of their leg and tested it against that painfully hot thermal probe. Little did they know, the researchers cranked down the heat each day; the participants thought the cream was working.

Another group was taught a kind of fake mindfulness meditation—they were told to breathe deeply for 20 minutes but were given no instructions on how to do it mindfully. The control group was subjected to 20 minutes of a very boring book on tape: The Natural History and Antiquities of Selborne.

For the real intervention, people sat for 20 minutes with straight posture, closed their eyes and listened to specific instructions about where to focus one’s attention and how to let thoughts and emotions pass without judgment. “Our subjects are taught to focus on the changing sensations of breath and to follow the breath with the mind’s eye as it goes down the chest and abdomen,” Zeidan says.

After four days, everyone re-entered the MRI machine and endured the same pain from the 120-degree probe. They were told to use their training—breathing deeply, mindfully meditating or the cream. They used a lever to indicate the physical intensity and emotional unpleasantness of the pain.

They found that people in all of the groups had greater pain reductions than the control group. The placebo cream reduced the sensation of pain by an average of 11% and emotional unpleasantness of pain by 13%. For the sham mindfulness group, those numbers were 9% and 24% respectively. But mindfulness meditation outperformed them all. In this group, pain intensity was cut by 27% and emotional pain reduced by 44%.

That shocked Zeidan. Past research has indicated that the opioid morphine reduces physical pain by 22%—and mindfulness had surpassed even that. But the MRI results, which showed how pain was registering in their brains, surprised him even more. People who had practiced mindfulness meditation seemed to be using different brain regions than the other groups to reduce pain.

“There was something more active, we believe, going on with the genuine mindfulness meditation group,” Zeidan says. This group had increased activation in higher-order brain regions associated with attention control and enhanced cognitive control, he says, while exhibiting a deactivation of the thalamus—a structure that acts as the gatekeeper for pain to enter the brain, he explains. “We haven’t seen that with any other technique before.”

It’s an important preliminary study, Zeidan says, but exactly who will benefit from meditation’s impact on pain is still unknown. “We’re now at the stage, at least in my lab, where we have enough evidence that meditation reduces pain and it does it in a really unique fashion, different from any other technique we’ve seen,” he says.

And as for the questions left unanswered? “We don’t have the studies yet,” he says, “but we’re getting there.”

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Write to Mandy Oaklander at mandy.oaklander@time.com.