Interestingly enough, there was a student at Harvard in the 1960's (recounted in the Varieties of Psychedelic Experience), who did a placebo-controlled study of psilocybin (see: http://en.wikipedia.org/wiki/Marsh_Chapel_Experiment).
Long term follow-ups seem to indicate that the differences (in terms of a self-report questionnaire, at least) were maintained over 25 years.
In the book at least, it was concluded (by the primary researcher) that the blinding was completely ineffective (though I don't think that this was confirmed with a manipulation check).
I would say that placebo-controlled studies of psychedelics, for similar reasons that placebo-controlled studies of other drugs (cigarettes, coffee, alcohol) will be difficult. Namely that a placebo should be identical to the treatment in every respect except for the active ingrediant, and what's the active ingrediant?
Its really well-worth checking out the Varieties for some good pointers to research in the 50's and 60's, there was quite a lot of it, and although some of it was methodologically unsound, and there are very few RCT's, the sheer amount of studies should probably carry some weight.
Long term follow-ups seem to indicate that the differences (in terms of a self-report questionnaire, at least) were maintained over 25 years.
In the book at least, it was concluded (by the primary researcher) that the blinding was completely ineffective (though I don't think that this was confirmed with a manipulation check).
I would say that placebo-controlled studies of psychedelics, for similar reasons that placebo-controlled studies of other drugs (cigarettes, coffee, alcohol) will be difficult. Namely that a placebo should be identical to the treatment in every respect except for the active ingrediant, and what's the active ingrediant?
Its really well-worth checking out the Varieties for some good pointers to research in the 50's and 60's, there was quite a lot of it, and although some of it was methodologically unsound, and there are very few RCT's, the sheer amount of studies should probably carry some weight.