You’ve seen them on display at health food stores and jewelry shops. You’ve read anecdotal testimonials like: “The best copper magnetic bracelet I’ve ever had!” You can order them online from thousands of commercial sellers.

But researchers from the U.K. have shown in the first randomized placebo-controlled trial that, no matter what claims their sellers may make, these metallic objects are in fact ineffective in treating pain. They say that any benefit derived from them can be attributed to psychological placebo effects.  “Our findings suggest that such devices have no real advantage over placebo wrist straps that are not magnetic and do not contain copper,” says Dr. Stewart Richmond of the University of York, the lead author of the study, published in the current issue of the journal, Complementary Therapies In Medicine.

However, Dr. Richmond emphasizes that although these products don’t necessarily cause harm, people should be careful about spending a lot of money on products that claim to cure your ailments with magnetic therapy.

What is a randomized placebo-controlled trial anyway?  It’s a way of testing a medical therapy in which, in addition to a group of subjects that receives the treatment to be evaluated, a separate control group receives a sham  “placebo” treatment which is specifically designed to have no real effect. Placebos, or ‘sugar pills’, are most commonly used in blinded trials, where subjects do not know whether they are receiving real or placebo treatment. Often, there is also a further “natural history” group that does not receive any treatment at all. The purpose of the placebo group is to account for the placebo effect.  This means any effects from treatment that do not depend on the treatment itself. Such factors include:

• knowing one is receiving a treatment
• attention from health care professionals
• positive attitude towards the drug/device being tested
• expectations of a treatment’s effectiveness by those running the research study

Without a placebo group to compare against, it’s not possible to know whether the treatment itself had any effect. Patients frequently do improve even with a placebo. The only other serious study on the effectiveness of magnetic or copper bracelets to reduce pain was back in 1976.  Doing a successful blinded study on magnetic devices, however, has been difficult because it’s relatively simple for participants to figure out at home if their bracelet is magnetic or not.

Read more about the U.K. study in Complementary Therapies in Medicine, or this lively debate over the study’s findings on the  Science-Based Medicine website.

To learn more about different forms of scientific research studies, visit Nagging 101.