Scientists at Virginia Commonwealth University in Richmond, Va., were concerned when a young man contacted their department last year complaining of a heart-pounding, hallucinogenic high he had neither expected nor wanted to have.

The team, led by the forensic toxicologist Michelle R. Peace, had published a study about mysterious ingredients in vaping liquids. That’s how the man, a graduate student Dr. Peace declined to name, knew to tell it about his experience.

He said he had vaped a liquid, from a company called Diamond CBD, that contained CBD, or cannabidiol. A compound reputed to have soothing properties, CBD has been marketed by the fast-growing cannabis industry as an ingredient in sleeping masks, kombucha, Carl’s Jr. burgers and Martha Stewart-backed dog treats. It is not supposed to cause a psychoactive experience.

Dr. Peace decided to run some tests of Diamond CBD vaping liquids, some from the graduate student and some bought from the manufacturer. In four of nine samples, all marketed on the company’s website as 100 percent natural, her lab discovered a synthetic compound, 5F-ADB. That ingredient has been linked by the Drug Enforcement Administration to anxiety, convulsions, psychosis, hospitalization and death.