Psychedelics can change a person’s perceptions and sense of self, which has promising medical applications. While more research is needed, including on adverse effects, psychedelics may reduce depression and other conditions. Hundreds of clinical trials have examined psychedelics, including for treating PTSD and depression. Researchers struggle to distinguish genuine effects of psychedelics from the placebo effect. The medical use of psychedelics also raises questions for policymakers about how to balance potential benefits with research limitations and patient safety.