Placebo Power

Optimists are no longer alone in promoting “mind over matter.” A compelling study claims there is chem-ical credence for the place-bo effect, at least in mask-ing pain.

University of Michigan at Ann Arbor neuroscientist Jon-Kar Zubieta, who led the work, says that people produce a natural painkilling chemical in the brain when they expect to experience relief. Researchers gave test subjects a slow, long, harmless injection of a pain-inducing salt solution into the jaw. When the injection began, the subjects were asked to rate their level of pain. As it continued, the researchers said, falsely, that they had just added pain-relieving serum into the solution. Subjects were asked again to rank their discomfort.

Throughout the episode, subjects’ brains were scanned using positron-emission tomography. It showed that in people who said they felt less uncomfortable, particular regions of the brain produced painkilling

endorphins right after the placebo was promised. The people who expected to get relief actually produced it.

The results “open a new avenue for understanding pain as a complex experience that is moderated by a type of emotional mechanism,” Zubieta says. If the mind can induce chemical changes in the brain, psychologists and physicians could possibly devise ways to prompt natural medication through the power of suggestion. If fruitful, the approach could be tried for a variety of conditions. “The idea is to harness these mechanisms,” Zubieta explains. “Ultimately you want people to be more resilient, to have more capacity to suppress a negative experience.” —Kiryn Haslinger

Estrogen Blues

Over their lifetimes, women are twice as likely to suffer clinical depression than men. Low or imbalanced hormone levels can prompt depression in either sex, and insuffi cient estrogen in wom-en has long been suspected. Now a comprehensive review of 30 years of research indicates that the trouble may not be low estrogen levels per se but sharp variations in those levels.

Estrogen balances often change signifi cantly during puberty and menopause, as well as during a woman’s monthly reproductive cycle. In each circumstance, when the level shifts, a woman may experience a greater chance of depression, says Stephanie L. Douma, a researcher with Natural Resources Canada in Ottawa, who conducted the work independently. Details will be published in the February 2006 issue of Advances in Nursing Science.

Douma says women who are experiencing mood problems and the doctors who may treat them may not be thinking about the fl uctuation scenarios and therefore may not be stabilizing estrogen at optimum levels.

The study also has implications for hormone replacement therapy, which many women undergo during or after menopause. For example, women may take hormone pills

only every third day to counter a higher potential risk for breast cancer that might be linked to too much medication. But that protocol means the hormone level never stabilizes, Douma says.

Douma hopes that the fi ndings will prompt more investigations into best practices for regulating estrogen and that doctors will more routinely monitor their patients’ levels. These measures, she says, will help keep estrogen-associated depression at bay. —Sarah Todd Davidson

10 SCIENTIFIC AMERICAN MIND

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The brain releases natural

painkillers when it thinks it is getting

outside help.