Strategies to assess physiological effects of meditation

With regard to the physiology of meditation, research designs can be divided into 3 categories:

1) Case studies of meditation featuring small numbers of participants in which there is no attempt to control for confounding variables. While these are useful for generating hypotheses, they do not provide scientifically valid insights into meditation’s purportedly unique effects.

2) Own-control studies use participants in time sequential series (ie ab, aba or similar designs) in which the “a” condition is pre-meditation or non-meditation and the “b” condition is meditation. The “a” and “b” conditions are then compared. These studies have generally demonstrated significant differences (interpreted to be in favour of meditation) but they suffer from substantial limitations because they compare meditation to non-meditation and then assume that any differences are due to meditation, whereas they may in fact be due to methodological factors not specific to meditation at all (such as rest, expectancy, researcher demand and environmental issues). Further, this design is vulnerable to the possibility that one condition might be contaminated by carry-over effects from the preceding condition. A further important consideration applies especially to the case of novices — if the meditator is not sufficiently skilled then they may have difficulty in generating physiological changes and the effects (although potentially real) may not become detectable.

3) Experimental control studies are much more reliable as they involve two independent groups in which one meditates and the other engages in a control activity such as rest. There are however, methodological difficulties associated with this approach as well. First, use of novices (who are introduced to meditation during the trial) may mean that the effects of meditation are not large enough to generate a detectable change. Second, while use of advanced meditators (those who have practiced meditation over many years) may ensure that the necessary magnitude of effect is achieved, the question of selection bias becomes a significant consideration.

An ideal strategy would involve an experiment in which participants are randomly assigned from the same sample to either a meditation or a control group. This approach is rarely feasible however, since it would conventionally require many months or even years of practice before the participants achieved competence. With such lengthy time-lines the accumulation of drop-outs may in any case lead to selection bias. Therefore, a reasonable compromise strategy might involve using experienced meditators and comparing them to non-meditators who have either been matched for parameters including interest in meditation, or have been randomly selected from the population. This latter design was selected for the study described in this chapter.

Dr Ramesh Manocha


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  3. Julie Smith

    I see the problem with all three designs, however a randomised contol trial would certainly be of benefit to test your research questions. Yes it would have to be a large trial to have the right power analysis, but think of the outcomes. You could do things like measurement of brain activity, during a meditation session (for all participants), this could be assessed by a blinded assessor. The only way to truly provide scientific evidence of such a trial would to be to do an RCT – it is definitely not impossible just alot of hard work to write a proper protocol and put it in place. Drop outs wouldn’t be too much of an issue if you had sufficient follow-up procedures. Besides no study is perfect and unless its something where you are close to a cure you will always have drop-outs – this to me simply proves it is a real life study. If during your power analysis you allow for a35-40% drop out rather than the 205 drop-out usually factored in you will have a great study.
    Personally I believe this is worth pursueing. After what I have seen and witnessed through the use of some of the alternative practices that clearly work I believe that more scientific proof is required to open up the sceptics minds.

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