Wednesday, August 22, 2012

Nocebo effect - the harm expectations can do.

A piece by Enck and Häuser in the NYTimes summarizes (and links to) their paper in Deutsche Ärzteblatt Internationa reviewing 31 studies on how fearful expectations can become self-fulfilling prophesies. (A nocebo effect is the induction of a symptom perceived as negative by sham treatment and/or by the suggestion of negative expectations. A nocebo response is a negative symptom induced by the patient’s own negative expectations and/or by negative suggestions from clinical staff in the absence of any treatment.) A few of the cases cited:
-a team of Italian gastroenterologists asked people with and without diagnosed lactose intolerance to take lactose for an experiment on its effects on bowel symptoms. But in reality the participants received glucose, which does not harm the gut. Nonetheless, 44 percent of people with known lactose intolerance and 26 percent of those without lactose intolerance complained of gastrointestinal symptoms.
-In one trial, the drug finasteride was administered to men to relieve symptoms of prostate enlargement. Half of the patients were told that the drug could cause erectile dysfunction, while the other half were not informed of this possible side effect. In the informed group, 44 percent of the participants reported that they experienced erectile dysfunction; in the uninformed group, that figure was only 15 percent.
-a group of German psychologists took patients with chronic lower back pain and divided them into two groups for a leg flexion test. One group was told that the test could lead to a slight increase in pain, while the other group was told that the test had no effect on pain level. The first group reported stronger pain and performed fewer leg flexions than the second group did.
-A doctor’s choice of words matters. A team of American anesthesiologists studied women about to give birth who were given an injection of local anesthetic before being administered an epidural. For some women, the injection was prefaced by the statement, “We are going to give you a local anesthetic that will numb the area so that you will be comfortable during the procedure.” For others, the statement was, “You are going to feel a big bee sting; this is the worst part of the procedure.” The perceived pain was significantly greater after the latter statement, which emphasized the downside of the injection.

1 comment:

  1. The article was also mentioned in this very nice piece on SkepticBlog: