I have since conducted many studies that lend clear support to the idea of mind/body unity.

In one study2, we talked to hotel chambermaids about exercise and their health. At the outset, they did not see their work as exercise, so we showed them that making a bed, for example, was like working on a machine at the gym and that every time they worked to tidy and clean a room, they were moving their bodies in ways that qualified as exercise.

This mindset—that they actually did get quite a lot of exercise—led to physically quantifiable changes. Without eating any differently or working any harder, they lost weight, and their body mass index and waist-to-hip ratio decreased. Even their blood pressure came down. 

Of course, a mindset change can go the other way, too. In my own life, an important personal example of this occurred when my mother was diagnosed with breast cancer.

The disease had taken over her body, and her prognosis was grim from the start. According to the doctors, she had only a few more months to live. I stubbornly tried to keep her spirits up and pretended that the nightmare would pass, but I was more or less the only one with this optimism. Everyone else seemed to see her as frail and doomed and treated her with kid gloves; no one pushed her to keep up her strength or prepare for a cancer-free life they didn’t believe she’d ever enjoy.

Then the unexplainable happened: My mother’s cancer vanished, and we were given reason to think it might stay that way. But the damage was done; she had let others’ beliefs about her health lead her to become weak and more helpless. When the cancer returned some months later, she succumbed to it.