You know, of course, about the placebo effect, in which patients report positive results from taking a mere sugar pill.  Turns out there is also something called a nocebo effect, too.  This is defined as a negative placebo effect. It happens, for example, when patients take medications and actually experience adverse side effects unrelated to any specific pharmacological action of the drug. The nocebo effect is associated with a person’s prior expectations of adverse effects from the treatment. In other words, if we expect a treatment to hurt us, cause harm, or make us feel sick – it likely will.

The U.K.’s bright and brainy Dr. Ben Goldacre of Bad Science describes this phenomenon in this short but entertaining presentation from last year’s irreverent Nerdstock tour (“Nine Lessons and Carols for Godless People).   He offers three “properly insane” examples of the nocebo effect. He tells us, for example, how placebos can not only make people feel better (the active placebo effect), but if warned about non-existent side effects before they take a harmless placebo, patients actually can develop these side effects.

One of the stories he tells is about a study in which asthma patients are put on a saline nebulizer, essentially a simple salt water mist that will neither hurt nor help asthmatics.  But when these research subjects are told that the mist contains an allergen, fully half of the group experience an asthma attack because of the harmless saline nebulizer.

Sit back and enjoy watching Dr. Ben Goldacre’s entertaining 5-minute BBC presentation.  See also: Amazing and Strange Examples of Placebo Miracle Effects

Warning: rapid-fire delivery and some racy language that may be offensive to some!