[jschwartzi]

It might be possible to do a double-blind study on meditation, but you would have to be incredibly strict about the procedure for achieving a meditative state, and you would have to select people who know nothing about "meditation" as a practice both to administer bouts of meditation and to participate in the study. Then your part in the study would be to teach the controls the "placebo" practice and to teach the non-controls the strictly-defined meditative practice, and to convince all of the participants that they're meditating either way.

[stolio]

Unless you're testing Zen meditation in which case the placebo group and the real group may not (should not?) be distinguishable from one another.

It's often taught as "just sitting" so by the time you get the control group to sit down, shut up and hold still for half an hour every day they're doing the practice. Heck, they may be doing it better than the Zen meditators because they won't have anything extra attached to it at all :)