It's interesting that they're analyzing this stuff properly, but it's rather dodgy because the psychedelic experience can't be measured by any mean. If they measured their brain activity during the trip and got information on how the drug affects the brain, good. Otherwise, all they got was a bunch of anecdotal evidence that is next to useless for proper medical/scientifical investigation.
"most of the volunteers said the experience had changed them in beneficial ways, such as making them more compassionate, loving, optimistic and patient.
Most people say the same thing after having any kind of experience that made them ponder about their life. For example, a major car crash that put them close to death.