Nocebo Effect Explains Unusual Side Effects

The placebo effect is a well-established medical phenomena, however some researchers believe that the nocebo effect may well be at work among some patients. Whereas placebo means "I will please" in Latin, Nocebo means, "I will harm", and according to Dr. Arthur J. Barsky and colleagues the nocebo effect may explain why some patients report side effects unrelated to the medication they are taking.

Results of the review of research linked to the nocebo effect revealed that pessimistic patients who were expecting to develop serious side effects to drugs were significantly more likely to develop them. Furthermore, study participants who were warned that the drug they were given could cause gastrointestinal side effects were much more likely to experience them, compared with those who had not been informed of possible side effects. While the nocebo effect may seem quite harmless, the researchers say that the non-specific side effects caused by the phenomenon could have serious consequences as they may cause patients to stop taking medications or physicians to stop prescribing effective drugs.

The researchers also found that a patient's knowledge about a drug, or the name, shape or color of a pill can influence non-specific side effects caused by the nocebo effect. Results of one study showed that more than 90% of people who had been classified as allergic to penicillin were, in fact not allergic to the drug, while another found that patients given blue placebo pills were more likely to report drowsiness than patients taking pink ones. The results of that study agree with that of another which found that patients tend to associate blue and green pills with sedatives, and red, orange, and yellow pills with stimulants

SOURCE/REFERENCE: The Journal of the American Medical Association 2002; 287:622-627