I worry that this is NIDA-funded. That institution has history of commissioning nonsense studies to maintain prohibitions. [1] They're also probably responsible for a series of (failed) propaganda pieces focused on maintaining an arbitrarily anti-drug culture [2]

1 http://www.ukcia.org/research/gettman.htm 2 https://slate.com/technology/2006/09/a-white-house-drug-deal...