The clinical study, to be published in the May 2002 issue of the American Journal of Psychiatry (Vol. 159, #5), is the first to identify, using positron emission tomography (PET), the specific brain regions that change with placebo response and compare them to brain regions that change with active drug intervention.
"What we found is that patients who responded to placebo and those who responded to an anti-depressant had similar, but not identical, metabolic changes in cortical (thinking) and limbic-paralimbic (emotional) regions," says lead investigator Dr. Helen Mayberg of The Rotman Research Institute at Baycrest Centre for Geriatric Care. The research was conducted at the University of Texas Health Science Centre at San Antonio.
In a previous landmark study, published in the same journal in 1999, Dr. Mayberg identified a "see-saw relationship" that needs to take place between the cortical and limbic areas in order for the depressed brain to get better. Like a thermostat, metabolism in the emotional regions needs to turn down while metabolism in the thinking areas needs to increase.
In this latest study, Dr. Mayberg found that while the placebo and drug responders showed remarkably concordant changes in the brain, the patients on active medication showed 'additional changes' in the brainstem, striatum and hippocampus.
"It could be that these additional changes facilitated by active drug are necessary to stay well over the long term," she says. "In other words, drug is a placebo-plus."
In this study -- a double-blind, placebo-controlled study of fluoxetine (trade name Prozac) -- 17 depressed, hospitalized men were given either the drug or a placebo over a six-week period. Neither the researchers nor patients knew who received
Contact: Kelly Connelly