Psilocybin is a serotonergic psychedelic derived from the Psilocybe genus of mushrooms.7 Both psilocybin and its active metabolite psilocin display high-affinity agonism for the 5-hydroxytryptamine (HT) 2A receptor (5-HT2A).7 Preliminary evidence suggests that serotonergic psychedelics are well tolerated and alleviate symptoms of depression in combination with psychological support (psilocybin-assisted psychotherapy (PAP)).8, –10 Prior research has demonstrated that 25 mg of psilocybin is a therapeutic dose for both major depressive disorder (MDD) and TRD.11, –13. This evidence concerns the gene HTR2A and major depressive disorder.