Placebos may induce improvements in brain function but may also
cause side effects—especially among psychiatric patients.
In one study, Andrew Leuchter, M.D., a professor of psychiatry at
the University of California, Los Angeles, found that 38 percent of
depressed patients who received placebos showed lasting mood improvement,
while some 52 percent of depressed patients who received medication
reported feeling better.
The placebo effect is well known, but this study was the first to
isolate neurological change. Control subjects who reported improvement
showed greater electrical activity and blood flow in the prefrontal
cortex, which is associated with mood and anticipation. Leuchter, who
published the findings in the
American Journal of Psychiatry, theorizes that
expectations are largely responsible for the improvement, noting that
people pursue treatment when mentally ready.
In a second study, negative expectations were found to be equally
powerful: Approximately one-fourth of patients taking placebos are
troubled by nonspecific side effects, according to a review in the
Journal of the American Medical Association.
Patients who are anxious or depressed are more likely to report negative
or nonspecific side effects, but as many as 80 percent of healthy
patients may experience the nocebo (Latin for "I will harm") effect, as
Aesthetic variables demonstrate the crude power of nocebos:
Patients given blue pills in one study were more likely to report
sedation than patients who received pink meds.
And a reality check can defuse even the most potent placebo. The
moods of Leuchter's buoyed subjects deteriorated when they discovered
they'd received bogus drugs.