So, I've read TFA, I see no citation, and I'm still Googling to track down the original research. They may not have made it up, but they may have taken it out of context or omitted details.

>> Have you known anyone who hasn't had a problem with either of those drugs but still used them at some point in their life?

No, I haven't. That's why I'm curious about whether the statistic is uniformly true, or averaged, or what. I'm not saying they made it up, I'm saying I'd like to see more details about how they arrived at that number.

edit: for instance, let's say 90% of "drug users" are marijuana users. Okay, then I'm not surprised, but that would only speak to the danger of marijuana compared to other drugs. Or is it 90% of the users of any given drug? I'd be surprised about the latter. Coming from the United Nations is not a shining banner of truth and unbiased facts.

Found it:

"Globally, it is estimated that in 2012, between 162 million and 324 million people, corresponding to between 3.5 per cent and 7.0 per cent of the world population aged 15-64, had used an illicit drug — mainly a substance belonging to the cannabis, opioid, cocaine or amphetamine-type stimulants group — at least once in the previous year.

The extent of problem drug use - by regular drug users and those with drug use disorders or dependence remains stable at between 16 million and 39 million people."

http://www.unodc.org/documents/wdr2014/World_Drug_Report_201...

Thanks - that report contradicts the quote in question. Their data shows that opiate consumption is relatively low world-wide compared to marijuana and other drugs, yet they state in the initial paragraphs that opiates are responsible for the majority if "problem drug users".