A Catholic priest, a Rabbi and a Buddhist walk into a bar and order some magic mushrooms. It may sound like the first line of a bad joke, but this scenario is playing out in one of the first scientific investigations into the effects of psychedelic drugs on religious experience – albeit in a laboratory rather than a bar.

Scientists at Johns Hopkins University in Baltimore have enlisted two dozen religious leaders from a wide range of denominations, to participate in a study in which they will be given two powerful doses of psilocybin, the active ingredient in magic mushrooms.

Dr William Richards, a psychologist at Johns Hopkins University in Baltimore, Maryland who is involved in the work, said: "With psilocybin these profound mystical experiences are quite common. It seemed like a no-brainer that they might be of interest, if not valuable, to clergy."