The power of suggestion

We're all familiar with the placebo effect, in which a sugar pill makes people feel better. Researchers have now identified a nocebo effect, in which suggesting side effects of a fake drug cause people to experience those effects.

If you tell a group of trial volunteers that they’re testing a new drug that may relieve the pain of migraines, a significant number of volunteers will experience pain relief after taking the drug — even if they’ve been randomly assigned to the placebo group and are receiving nothing but sugar pills. The placebo effect in action. 

But here’s where it gets interesting. If you tell the volunteers that the side effects of this new medicine may include dry mouth, tingling in the hands and feet, and slight dizziness, some volunteers will experience precisely these side effects — inboth groups. In fact, some volunteers who are taking nothing but sugar pills will be made so uncomfortable by these symptoms that they will choose to drop out of the trial early.

The relevance of the nocebo effect is not limited to clinical trials.

A particularly nasty demonstration of its power can be provided by patients who are being treated for Parkinson’s disease with small doses of electrical current delivered to certain structures in the brain. This technique, known as Deep Brain Stimulation (DBS), has been shown to be effective in controlling tremor and other motor issues in patients who are resistant to drugs. But if you tell a DBS patient that the current has been switched off — even though it remains on — their coordination and other motor functions will abruptly decline until you tell them that the juice has been switched on again. Classic nocebo.

Someone suggested that I look tired and will probably need a nap this afternoon. Wow, they're right!