What the researchers tested
Laprairie and colleagues examined CBD’s effects on CB1 signaling in laboratory cell models. CBD reduced responses to THC and 2-AG in the pathways they measured, supporting a negative allosteric-modulator interpretation under those conditions. Original paper.
What that does—and does not—mean
Allosteric modulation changes how a receptor responds to another compound. This experiment helps describe a possible mechanism; it does not establish every effect of CBD in people. It was not a clinical trial showing that a particular CBD dose prevents intoxication, anxiety or psychosis from THC. Moving from a cell experiment to treatment advice requires separate evidence about exposure, outcomes and safety in people.
Original research
R B Laprairie; A M Bagher; M E M Kelly; E M Denovan-Wright. Cannabidiol is a negative allosteric modulator of the cannabinoid CB1 receptor.British journal of pharmacology (2015).