A clinical trial patient plops onto a sofa, slips on shades and receives a psychedelic drug as soft music plays in the background.  As our neuronaut soon spirals through the astral plane, what could possibly go wrong?

Plenty, it turns out—from heart complications to intense perceptual disturbances. The U.S. Food and Drug Administration late last month provided the health care industry welcome guidance that could mitigate legal risks as researchers increasingly explore psychedelics for use in prescription drugs and therapies.