Placebo effect significant in
treating depression
(October 5, 1998)
The effectiveness of antidepressants is mainly
in the placebo effect of treatment, not in the medication
itself, according to a new study by Irving
Kirsch.
Seventy-five percent of the response to
medication for depression was a result of the patient
being in treatment, while at the most 25 percent of the
response was a true drug effect, asserts the study by
Kirsch, a professor of psychology, and former UConn
graduate student Guy Sapirstein.
"This means that for a typical patient, 75
percent of the benefit obtained from the active drug
would also have been obtained from an inactive placebo,"
Kirsch says. "Whether the remaining 25 percent of the
drug response is a true effect of the drug or a
psychologically triggered response to side effects alone
cannot yet be determined."
More placebos have been administered to research
participants than any single experimental drug.
"However, although almost everyone controls for
placebo effects, almost no one evaluates them," he says.
"With this in mind, we set about the task of evaluating
the magnitude of the placebo response to antidepressant
medication."
The study analyzed the possibility that
antidepressants serve as active placebos, which produce
side effects but do not cause any actual drug effect on
the problem.
"Data from other studies indicate that most
participants in studies of antidepressant medication are
able to deduce whether they have been assigned to the
drug condition or the placebo condition," according to
the study.
"This study suggests that antidepressants might
function as active placebos, in which the side effects
amplify the placebo effect by convincing patients that
they are receiving a potent drug," Kirsch says. "So if a
patient takes a pill that causes side effects, he or she
feels better because they believe they have been given an
actual antidepressant and that the pill must be
working."
The study, Listening to Prozac but Hearing
Placebo: A Meta-Analysis of Antidepressant Medication,
was published in the electronic journal Prevention &
Treatment, http://journals.apa.org/prevention/, a
publication of the American Psychological
Association.
Kirsch and Sapirstein analyzed the changes in
2,318 patients whose primary diagnosis was depression and
who had been randomly assigned to either antidepressant
medication or placebo in 19 double-blind clinical trials.
Sapirstein, a graduate student when they conducted the
study, is now a psychologist at Westwood Lodge Hospital
in Needham, Mass.
The study was a meta-analysis, a way of
mathematically combining results from different studies
with different measures. The analysis included 19 studies
in which a total of 858 participants received placebos
and 1,460 participants received medication. Medication
included antidepressants such as Prozac and imipramine
and potentially active placebos such as
lithium.
Renu Aldrich
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