Many people use copper bracelets and magnetic wrist straps to alleviate the pain of arthritis, but a new randomized, double-blinded, placebo-controlled study concludes they do not work.

British researchers randomized 65 patients with rheumatoid arthritis to receive one of four treatments: wearing a powerful magnetic wrist strap, a weak magnetic strap, a non-magnetic strap and a copper bracelet. Each patient wore each device for five weeks and completed pain surveys. The study appears in the September issue of PLoS One.

The patients reported pain levels using a visual scale, ranging from “no pain” to “worst pain ever,” and recorded how often their joints felt tender and swollen. Researchers used questionnaires to assess physical limitations, and tested for inflammation by measuring blood levels of C-reactive protein and plasma viscosity.

There was no statistically significant difference in any of these measures regardless of which type of device patients were wearing.

Stewart J. Richmond, a researcher at the University of York who led the study, acknowledged that the devices may have some benefits as a placebo.

“People swear by these things,” he said. “Is it ethically correct to allow patients to live in blissful ignorance? Or is it better to provide them with the facts? We can’t deceive patients. We have to be honest with them.”