In a self-blinded microdosing study, the majority of the observed effect was attributed to the placebo response.

“So he controlled for expectancy. So people's positive expectancy, which is, in a sense, the vehicle that carries the placebo response. It's why you have a placebo. Is that positive expectancy can drive a therapeutic effect to a large extent. So you measured that pre-trial and then used it to correct for the response. And how did it work? Those who got a placebo but thought they got a microdose did as well as those who thought they got a microdose and did get a microdose. So it was the bigger effect-- the majority of the effect was in thinking that you got a microdose.”