Many studies were undertaken in the 1950's and 1960's in the US, by the likes of Timothy Leary and Richard Alpert (now known as Ram Das) among others. Those studies came to an abrupt halt due to political reasons, but thankfully in the last few years there has been renewed interest in seeing how hallucinogenics can be consciously used to induce a mystical experience which can be life-changing.
Anthony Bossis of New York University has been studying the effects of using psilocybin on terminally ill cancer patients to see if it can alleviate some of the anxiety around death and dying for these patients. The results have been nothing less than staggering.
There's an article in the New Yorker here.
And a great interview and story here on CBC's wonderful radio program, Tapestry.