Placebo gives brain emotional break
By Bruce Bower
The placebo effect, in which people experience health benefits from inactive medications, thrives on great expectations. According to a new study of placebo-induced reduction of anxiety, such expectations trigger a decline in the brain’s emotional responsiveness and marshal pain-numbing neural activity.
A team led by Predrag Petrovic of the Karolinska Institute in Stockholm tested 15 women over 2 days. On the first day, each volunteer used a scale of 1 to 100 to rate the unpleasantness of pictures presented to her. For example, a picture of severely injured people got high rankings and a landscape ranked low. Participants then received low intravenous doses of an antianxiety drug and rated the images a second time. Finally, the women rated the same images after receiving intravenous doses of a substance that blocked the antianxiety drug’s effects.