As the AIDS epidemic took hold in this country, doctors noted that introverted victims were more likely to die than outgoing, extroverted ones. A "melancholy" temperament has long been linked to bad health outcomes. Now there’s a study "that pinpoints the biological mechanism that connects personality and disease," says Bruce Naliboff, a researcher at the UCLA Neuropsychiatric Institute in Los Angeles. It’s his study doing the pinpointing–which may not be as precise as he claims–and it appears this week in the journal Biological Psychiatry.
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Shy or introverted people tend to be more jumpy when confronted with new situations. Their nervous systems react strongly. So Naliboff and his colleagues did some mental and physical confrontation of a group of 54 HIV-positive men, all in good health at the start of the study. The doctors tried to startle the men with a tiny "beep" sound. Some jumped–heart rate increased, the skin became more moist and more flushed–and some didn’t. Then there were sudden requests for brief physical exercise and mental pop quizzes. Reactions to these challenges were also measured in terms of skin, heart, and blood responses. In this way, researchers gave each man a reactivity score–basically a rating of how rattled they became.
The scientists followed the men for 12 to 18 months, measuring how fast HIV replicated in their bodies and their levels of T cells (which HIV destroys). The shy, more easily rattled people had more of the virus. They also lost T cells. Some of these people started anti-HIV drugs during the study, but the medicine barely made a dent in the growing virus. The more extroverted people, however, did respond to the drugs.
The main biological response underlying these stress reactions is the release of a chemical called norepinephrine, which triggers the body’s "flight or fight" response. The UCLA team has found, in another study, that the chemical leaves T cells vulnerable to infection. This, the researchers suggest, is how stress sabotages the struggle against illness in shy people: Repeated waves of norepinephrine weaken T cells and the immune defense system. This is moving beyond oft-repeated claims that stress causes illness. It’s a theory about how stress, in certain people, can have biological effects that end up with the growth of an illness-causing organism.
Still, this is where the research lands a little wide of a pinpoint. It’s not clear what the chemical does to T cells that leaves them more vulnerable to a virus, and until that’s nailed down the link between cause and effect isn’t closed. However, this is an elegant demonstration of how closely the mind and body might work in their reactions to a deadly disease.
