Thursday, May 14, 2009

Mind games

The placebo effect:

Several times a day, for several days, you induce pain in someone. You control the pain with morphine until the final day of the experiment, when you replace the morphine with saline solution. Guess what? The saline takes the pain away.

This is the placebo effect: somehow, sometimes, a whole lot of nothing can be very powerful.

The nocebo effect:

The placebo effect has an evil twin: the nocebo effect, in which dummy pills and negative expectations can produce harmful effects. The term "nocebo", which means "I will harm", was not coined until the 1960s, and the phenomenon has been far less studied than the placebo effect. It's not easy, after all, to get ethical approval for studies designed to make people feel worse.

An interesting knowledge asymmetry is developing in the mind-body science: due to ethical considerations, we will know a lot less about harmful nocebos than harmless placebos.

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