Power of Positive Thinking May Have a Health Benefit, Study Says

Most people accept the idea that stress and depression chip away at the body’s natural ability to fight off disease. But many medical scientists have remained skeptical that the mind can exert such a direct influence over the immune system.
In recent years, however, evidence has accumulated that psychology can indeed affect biology. Studies have found, for example, that people who suffer from depression are at higher risk for heart disease and other illnesses. Other research has shown that wounds take longer to heal in women who care for patients with Alzheimer’s disease than in other women who are not similarly stressed. And people under stress have been found to be more susceptible to colds and flu, and to have more severe symptoms after they fall ill.

Now a new study adds another piece to the puzzle. Researchers at the University of Wisconsin are reporting today that the activation of brain regions associated with negative emotions appears to weaken people’s immune response to a flu vaccine.
“It’s the first time that the brain has really been brought into the picture,” said Dr. Richard J. Davidson, director of the university’s Laboratory for Affective Neuroscience and a senior author of the report, which appears in The Proceedings of the National Academy of Sciences.

During a task that required experiencing negative emotions, greater electrical activity in the brain’s right prefrontal cortex predicted a weaker immune response six months later, as measured by the subjects’ level of antibodies to the flu shot, the researchers found. Greater activation in the left prefrontal cortex was associated with a stronger immune response.
In earlier work, Dr. Davidson and his colleagues have found that regions of the right prefrontal cortex are active during emotional responses involving anger, fear and sadness. The left prefrontal cortex appears to be more active in association with positive emotions, like feeling enthusiastic and upbeat, according to the research.

Dr. Janice Kiecolt-Glaser, a professor of psychiatry at Ohio State University College of Medicine and an expert on stress and immunity, said the new study was “some of the best evidence we’ve seen to date.”

“They have a very nice link to what happens if you meet a bacterium or a virus in real life,” she said, “and they’re saying that if you have the response style you’re talking about here, you’re going to be at greater risk for getting it.”
In the study, 52 women, ages 57 to 60, were asked to think and write about extremely positive and extremely negative events in their lives. The women were participants in a continuing long-term study of high school graduates from the class of 1957.
In the positive emotion condition, the women were instructed to spend one minute recalling an experience of “intense happiness or joy, specifically the best time or experience in their life,” and then to spend five minutes writing about it. In the negative emotion condition, the subjects did the same for an event that inspired “intense sadness, fear or anger, the worst time or experience in their life.”

Electrical activity in the brain’s prefrontal cortex · an area known to be centrally involved in emotion · was recorded by electroencephalogram while the women were thinking about their experiences and after the writing ended. Then the participants were given a flu vaccine.
Six months later, the researchers found, the subjects who showed the most activity in the brain’s right prefrontal cortex also had the lowest antibodies. Brain activation during the positive-emotions condition was not linked to differences in antibody levels.

Dr. Davidson said it was not clear what factors accounted for the differences in brain activation and immune response, but genetic and environmental influences might play a role.
Still, he added, the findings offered hints to how a person’s mood might ultimately affect susceptibility to illness. The right prefrontal cortex, for example, communicates with certain types of immune cells, and stress appears to alter the functioning of a chemical messenger, dopamine, in the region. In addition, the right prefrontal cortex interacts with the hypothalamic-pituitary-adrenal axis, a major player in the body’s stress system, which in turn is linked to the immune system.

“The brain has the capacity to modulate peripheral physiology,” Dr. Davidson said, “and it modulates it in ways that may be consequential for health.”

But he also cautioned against overstating the power of mind over body in producing illness. There is no evidence, for example, that cancer is caused or affected by negative moods or attitudes, and many illnesses, Dr. Davidson said, may be unaffected by the neural changes set off by stress.

This is one factor among a whole host of factors,” he said, “and very likely it is not the most important one.”

September 2, 2003
Copyright 2003 The New York Times Company