When Dr. David Spiegel emerged from a three-hour shoulder surgery in 1972, he didn’t use any pain meds to recover. Instead, he hypnotized himself. It worked—to the surprise of everyone but Dr. Spiegel, who has studied hypnosis, a state of highly focused attention and intense concentration, for 45 years. Patient using very little pain medication, he remembers reading from his chart when he snuck a peek. We mustn’t have cut many nerves.

“There’s an incision from the top to the bottom of my shoulder, so they cut plenty of nerves,” Spiegel says now. “I was just handling the pain myself.”

Being hypnotized feels like what happens when you become so absorbed in a movie that you forget you’re watching one at all, like you have entered an imagined world, Spiegel says. This trance-like state, in which you’re more open and suggestible than usual, can be an effective tool to control pain, ease anxiety, quit smoking and deal with stress, trauma and even hot flashes, research shows. How it does that is what Spiegel, professor and associate chair of psychiatry and behavioral sciences at the Stanford University School of Medicine, and his colleagues wanted to find out in their new study published in the journal Cerebral Cortex.