High Dose THC Produces Effects Hard To Distinguish From Psilocybin

Study Design and Participants

High doses of THC from marijuana may have psychoactive effects that are hard to distinguish from those caused by the psychedelic psilocybin, according to a new study. The research, conducted by investigators with the Johns Hopkins University School of Medicine, involved four adults who underwent three or four sessions during which they were given either 25 milligrams of psilocybin, 25 milligrams of THC, 50 milligrams of THC or a placebo.

The THC was administered either as a synthetic form, dronabinol, or as a whole-plant cannabis distillate extract. Participants were told that ketamine, dextromethorphan, DMT and MDMA could also be administered, but they weren’t actually used during the study.

Both the participants and the facilitators of their sessions were blinded to what was actually received at the time, and they were asked to guess afterwards.

Key Findings

Every participant was able to correctly guess when they had received a placebo or when they had received the real psychedelic. However, “the 25 mg dronabinol condition was rated as more similar to a classic psychedelic or dissociative than a cannabinoid, while the 50 mg distillate condition was perceived as predominantly sedative- or dissociative-like, but also moderately like a classic psychedelic by the one participant who received it,” the researchers wrote.

Implications for Psychedelic Research

The results, researchers said, could have implications for future clinical trials of psychedelics by helping to address the problem of “unblinding,” where participants are able to tell whether they have received the drug being tested, a placebo or a comparator substance.

That issue could potentially be avoided by administering cannabis products to participants in the non-psychedelic control group, the new paper indicates. The researchers said the findings suggest that appropriately dosed THC may help reduce functional unblinding in randomized clinical trials of psychedelics compared with placebo and other active comparators.

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