Link to the full study: https://www.biorxiv.org/content/early/2018/08/08/384412 I have not read it completely yet, but it seems it lacks any sort of blind trial and control group; hence, it fails to account for placebo effect. Given the nature of the experiment, I believe placebo effect could have significantly altered the results.
At best, this falls into the "quite interesting should probably do a proper follow up" pile.
One interesting line from the study. It says "that we did not use a control group (for obvious ethical and practical reasons)". Practical I get, there were only 38 of them in total. But ethical? What are the ethical concerns with not giving people a micro dose of hallucinogenic truffles?