Focus on Alternative and Complementary Therapies
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Focus Alternat Complement Ther©2005 Pharmaceutical Press
Focus Altern Complement Ther 2003; 8: 130–1
To systematically review the evidence from randomised controlled trials for cumulative effects of transcendental meditation (TM) on cognitive function.
Literature searches were made of electronic databases and collected papers and official websites of the TM organisation. Randomised controlled trials with objective outcome measures of the cumulative effects of TM on cognitive function were included. Trials that measured only acute effects of TM, or used only neurophysiological outcome measures were excluded.
A total of 107 articles reporting the effects of TM on cognitive function were identified and 10 met the inclusion criteria. Most were excluded because they used no controls or did not randomise subjects between treatments. Of the 10 trials included, four showed large positive effects of TM on cognitive function, four were negative, and two reported only limited positive effects. All four positive trials recruited subjects from among people favourably predisposed towards TM, and used passive control procedures. The other six, largely negative trials, recruited subjects with no specific interest in TM, and five used structured control procedures.
The strong association between positive outcome, subject selection procedure and control procedure indicates that the large positive effects reported in four trials are the result of a placebo effect. The claim that TM has a cumulative positive effect on cognitive function is not supported by the evidence from randomised controlled trials.
