I haven't tried microdosing, though I don't doubt that psychotropic medications, natural or otherwise, can have a very real effect on people. Depending on the person, it can be positive or negative. For example, I smoked some weed once with my friend and then showed him my TT robot. I demonstrated a drill I was working on (and kinda sucking at it), and boy did I all of a sudden become a master! Everything slowed down, I thought nothing, and just did it. Timing, contact, everything was perfect. I thought I would suck so much more being high, but the exact opposite happened.
Now, as for the scientific evidence for microdosing, I have to say it's pretty weak. Stamets is basing his conclusions on this article:
Psilocybin microdosing involves repeated self-administration of mushrooms containing psilocybin at doses small enough to not impact regular functioning. Microdose practices are diverse and include combining psilocybin with substances such as lion’s mane mushrooms (Hericium erinaceus; HE) and...
www.nature.com
You can read through it, I did and I find the scientific rigor rather lacking. There was no blinding, people can choose whichever intervention they wanted, and as far as I can tell there is no limitation on what other things the participants can take. The potential for bias is simply enormous. Also concerning to me is both a lack of longer follow up (only 22-35 days in the study) and a complete absence of an analyses of potential side effects.
I think things like psylocybin have potential, but there is some evidence that it can cause long lasting alterations to your brain chemistry. The problem to me is that we don't have enough information on whether if that is good or bad. A long term trend toward less anxiety would be good, a long term trend toward hallucination prone would be bad, for example. Would you like to commit to a potentially permanent alteration of your brain without knowing what it may do, or at least what it'd most likely do? At this point I wouldn't, but I I'll be keeping an eye on this subject as psychedelics become more mainstream.