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Nocebo Effect
The nocebo effect is the conceptual
opposite of the placebo effect and can be defined as the harmful effects seen in
a person that occur in response to treatment (i.e. a placebo) but cannot be
considered due to the specific treatment used. The word nocebo in Latin "I
will harm". Some researchers argue that the nocebo effect is as important
as the placebo effect when conducting clinical trials and research into new
therapies. Interestingly there are reports that some studies of the
placebo effect ignore reports of negative results related to the placebo
treatment, which undoubtedly leads to an overly positive view of the placebo
response rate. The nocebo effect has been implicated as a possible
explanation for the large number of side effects seen with drug therapies.
A study comparing sham acupuncture to inert pill had the following negative side
effects associated with the placebo treatments (shown in percentage of
patients): Sham acupuncture: Pain during treatment (15),
Increased pain after “removing” needle (10)Redness or swelling (3), Other (12)
Placebo pill:
Dizziness (5), Restlessness (7), Dry mouth (19), Drowsiness (20),
Headache (4), Anxiety (4), Nightmares (3), Nausea (3),
Frequent urination (2),
Skin rash (2). The authors in this study further state that the side effect
profile of the placebos mimicked the listed side effects in the consent forms
used in the study.
Perhaps the most
well known example of the nocebo effect in medicine was the observation during
the Framingham Heart Study that women who believed they were prone to heart
disease had a four times higher risk of death than women with the same risk
factors who did not believe they were prone to heart disease. Another
study showed the power of the nocebo effect by administering sugar water to a
classroom of college students and telling the students that the mist was a
powerful emetic, 80% of the students threw up. A second study involving
college students involved telling 34 students that a non-existent electrical
current was being passed through their head and may cause a headache, 66% of the
students reported headache. A recent review of 109 double blinded trials
showed adverse effects following placebo administration in 19% of patients
overall (Rosenzweig). This study also found that rates of adverse events
were higher with more frequent dosing (28%) and in elderly patients (26%).
Although clinically
it may be as important as the nocebo effect there are far fewer studies looking
into the physiologic or psychological basis of the nocebo effect. |
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