|5 May 2002 @ 07:59|
Prozac placebos 'do trick for depressed patients'
Depressed patients tricked into thinking they are being treated undergo healing brain changes similar to those produced by Prozac, scientists have found.
The discovery is conclusive proof of the power of the "placebo effect" - the mind-over-body influence of believing that a drug will work.
Patients given a dummy pill containing no active ingredients experienced brain changes remarkably like those induced by Prozac, the world's most popular antidepressant.
In the first study of its kind, scientists at the University of Texas, San Antonio, US compared brain scans of depressed patients either given Prozac or a placebo pill.
Seventeen depressed, hospitalised men took part in the study. Neither the patients nor the researchers knew who received the placebo until after the experiment.
The positron emission tomography (PET) scans tracked a radioactive form of the body fuel glucose to pinpoint which areas of the brain were most or least metabolically active.
Both groups of patients shared a pattern of increased activity in the cortex - the "thinking" part of the brain - and decreased activity in the limbic regions which govern emotion.
The researchers pointed out that such a response was necessary for a therapeutic benefit.
Of the 15 patients who completed the six-week study, eight showed improvement in their symptoms, half of whom had received the placebo.
Chief investigator Dr Helen Mayberg, from the Baycrest Center for Geriatric Care in Ontario and the University of Toronto, Canada, said: "Our findings are consistent with the well-recognised placebo phenomena that 'expectation' that a treatment w ill be helpful is a critical part of the therapeutic relationship between a patient and their doctor."
However, there were important differences between the way the two sets of patients responded.
Those who took Prozac experienced additional changes in lower areas of the brain - the brainstem and hippocampus - not seen in the placebo group.
The researchers, who reported their findings in the American Journal of Psychiatry, said the increased activity in these regions probably helped to sustain the cortical and limbic changes.
"It could be that these additional changes facilitated by the active drug are necessary to stay well over the long term," said Dr Mayberg. "In other words, the drug is a placebo-plus. If you respond to a placebo, this may mean that your brain has an inherent capacity to heal itself - but it is likely to be a short-term effect."
Previous studies had shown that patients who have responded to placebos tend to relapse sooner than those given active drugs.