From TIME magazine:

Research suggests that the psychedelic drug MDMA, an empathogenic stimulant also known as Molly or ecstasy, can spark changes in the brain that induce a childlike state of neuroplasticity and help forge new neural connections.

(It could well be approved for PTSD by the U.S. Food and Drugs Administration in August after two advanced stage trials showed significant benefits.)

Researchers are also studying other psychedelics as well, like the powerful drug ibogaine.