To carry out an independent, systematic review of randomized clinical trials of Transcendental Meditation (TM) for cumulative effects on blood pressure.
Searches were made of electronic databases and the collected papers and official web sites of the TM organization. We included only randomized clinical trials, without confounding co-interventions, which measured the cumulative effects of TM on blood pressure.
Six trials met the inclusion criteria but one, reported only in abstract form, could not be evaluated. Procedures for establishing baseline blood pressure were adequate in only one trial. Only one of the trials included a follow-on assessment and only one of the evaluable trials tested the effect of TM in hypertensive individuals. Three of the five evaluable trials reported statistically significant differences between intervention groups favouring TM and two found no significant differences between intervention groups. None of the five studies was conducted by independent authors without any affiliation to the TM organization.
All the randomized clinical trials of TM for the control of blood pressure published to date have important methodological weaknesses and are potentially biased by the affiliation of authors to the TM organization. There is at present insufficient good-quality evidence to conclude whether or not TM has a cumulative positive effect on blood pressure.
Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth, 25 Victoria Park Road, Exeter, Devon EX2 4NT, UK.
Correspondence and requests for reprints to Dr Peter H. Canter, Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth, 25 Victoria Park Road, Exeter, Devon EX2 4NT, UK. e-mail: firstname.lastname@example.org
Previously presented as a poster at the 10th Annual Symposium on Complementary Health Care, Royal College of Physicians, London UK, 21–22 November 2003.
See editorial commentary on page 2057
Received 5 March 2004 Revised 12 May 2004 Accepted 8 June 2004