Psychedelics, (hallucinogens), and all psychoactives, (even THC), tend to clear filters in the neuropathways that allow subconscious thoughts to be processed consciously. This sometimes leads to the "bad trip" (or paranoia in the case of the milder psychoactives). On the other hand, if a person is acclimated to the effects, (much easier to do with LSD or psylocibin than THC, provided the drug itself is not "bad"), the effects are generally a deeper understanding and perception on many matters.
LSD and psylocibin have been used from about 1950-1970 for treating addictions, OCD, etc, and have proven very effective. The Nixonian Comprehensive Drug Abuse Prevention and Control Act of 1970 made such substances schedule 1, (the most "dangerous", according to this draconian law) illegal, and treatments using them all but ceased, until recently. That law was mostly an anti-liberal attack on those opposing the Vietnam war. It made it easy to imprison those opposed to the US government's actions. Don't get me started...
To answer Smiddy's question with all due respect, Steve Jobs, (and likely a good number of Silicon Valley), have used such substances to their creative merit. They are good way to bridge left/right brain thinking actually.
I will neither confirm or deny any personal use, of course...;-)