HTR2A and Visual hallucination: The commonly referenced overarching mechanistic neurobiological principle is that psilocybin acts as an agonist of the 5-Hydroxytryptamine 2A receptor (5-HT2AR), which has been convincingly demonstrated as necessary for psychedelic drug effects [10,11,12], specifically for the propensity to visual hallucinations associated with psilocybin [13].