Exploration of the validity of weak magnets as a suitable placebo in trials of magnetic therapy.
OBJECTIVE
To investigate whether 50 mT magnetic bracelets would be suitable as a placebo control condition for studying the pain relieving effects of higher strength magnetic bracelets in arthritis.


METHODS
Randomised controlled comparison between groups given either a weak 50 mT or a higher strength 180 mT magnetic bracelets to test.


METHODS
Four arthritis support groups in Devon, UK.


METHODS
One hundred sixteen people with osteoarthritis and rheumatoid arthritis.


METHODS
Beliefs about group allocation and expectation of benefit.


RESULTS
There was no significant difference between groups in beliefs about allocation to the 'active magnet' group. Participants were however more likely to have an expectation of benefit (pain relief) with the higher strength magnetic bracelets.


CONCLUSIONS
Asking about perceived group allocation is not sufficient to rule out placebo effects in trials of magnetic bracelets which use weak magnets as a control condition. There are differences in expectation of benefit between different magnet strengths.
Peninsula Medical School (Primary Care), St Luke's Campus, Exeter EX1 2LU, United Kingdom. Colin.Greaves@pms.ac.uk <Colin.Greaves@pms.ac.uk>
C J
CJ
Greaves
T N
TN
Harlow
D000368:Aged; D001172:Arthritis, Rheumatoid / Q000628:therapy*; D001294:Attitude to Health; D005260:Female; D006801:Humans; D008280:Magnetics / Q000627:therapeutic use*; D008297:Male; D009354:Neodymium; D010003:Osteoarthritis / Q000628:therapy*; D015990:Placebo Effect; D015203:Reproducibility of Results; D012107:Research Design
D009354:Neodymium