Well I assumed by the title that we were not talking about chemotherapy but about the use of chemical compounds that effect the electro-chemical state of the body producing sensations ranging from relaxation, to pleasure, to euphoria and to time/space distortions for the stated goal of recreation.
And I don't ever say anything about drugs without saying that first, because I don't ever want anyone thinking I'm promoting, encouraging or advocating that other people do such things. I grew up in the San Francisco Bay Area in the late 60s/early 70, and I've worked in show biz and academia for decades (both over-run with drugs) and I can honestly say I don't know anyone who was really all the better for doing any of that. Its not an instant road to ruin for all, most people do some, have fun, walk away. But for others.....? I dare not go there. Most - say in the 90 percentile - of the people I know who have done say, cocaine, its been a nice fun time. But for the single digit percentage, it was like taking a loaded gun, sticking it in their mouth and pulling the trigger. Their life was in some ways over at that minute. And you never know who its going to be. You never know if that number comes up with drinking, or smoking, or toking, or this pill or that one, or this power. Why take the risk when there is so little to gain?
And its not even the 'drugs will kill you' deal. Most of the people I know who really messed up their life with drugs did so because they made some really incredible stupid decisions while under the influence.
That being said, and I'm going to say this as plain as I can, people like to get ->-bleeped-<-ed up. There are examples in the animal kingdom besides us, but we are the kings of the forest on this one. The oldest recipe on record is from an Egyptian papyrus and its a recipe for beer. Matter of fact, we have lots and lots of old recipes for things like beer and wine. We found out how to do that stuff in pre-history. We have never forgot how. The use of psychoactive plants has been around since pre-history, as has the smoking of marijuana. Face it, people like to tie on on, rev it up, overindulge. Its nothing new. People act as if massive drug abuse is something in the 20th century, but face it, how drunk were the people in Rome for the blood sports - I bet they were wicked drunk.
I'm not at all sold on the 'mind opening' aspect, and if its true, its only true for a very few drugs, the first couple of times you take them.