The effects of psilocybin on the brain could also help treat mental illness and lead to personal growth.
"The fact people can be this open after just a couple of sessions has implications for psychotherapy to try and speed it up and to treat all sorts of mental disorders," said Ross.
"The domain of openness generally has benefits related to overall intelligence, the ability to think abstractly and creatively and to have an active imagination," said MacLean.
But MacLean added that the subjects in her study were very open to begin with, spiritually active and most held post-graduate degrees, so it was difficult to say whether the same effects would be seen in the general population.
She also cautioned that psilocybin was administered under very carefully monitored circumstances. Psilocybin in previous studies, she added, caused anxiety and fear in some people who participated.
"The problem with these hallucinogenic drugs historically is that they escaped from laboratories and people started using them without paying attention to their special qualities," said Ross. "That can be very problematic and dangerous."
"The implications are strictly for this kind of controlled setting," said Grob. "They do not transfer over to the regular world."
Psilocybin is an illegal drug. The U.S. Drug Enforcement Agency considers it a Schedule 1 drug, meaning the potential for abuse is high, it has no medically accepted use and isn't considered safe to use under medical supervision.
Its use in laboratories is strictly regulated, and psilocybin can only be manufactured in facilities certified by the DEA.
Ross said under the right conditions, psilocybin is safe with no known toxic effects.
But Dr. Daniel Angres, associate professor of psychiatry at Rush University Medical Center, argued the use of psilocybin is too risky.
"There are safer ways to create profound transcendent experiences, like the use of meditative states, that can facilitate therapeutic openness and change," he said.
He also doesn't believe drug-induced personality changes can be sustained in the long run.
"Character can and will deteriorate with the use of substances that have abuse potential over the long run," he said, "even though initially there may sometimes seem to be 'positive personality adaptations.'"