LONDON – Marijuana is the most popular illegal drug used worldwide, but addictions to popular painkillers like Vicodin, Oxycontin and codeine kill the most people, according to the first-ever global survey of illicit drug abuse.

In addition to cannabis and opioid painkillers, scientists analyzed abuse of cocaine and amphetamines in 2010, largely based on previous studies. Ecstasy and hallucinogens weren’t included, for lack of data. The researchers found that for all the drugs studied, men in their 20s had the highest rates of abuse. The worst-hit countries were Australia, Britain, Russia and the U.S. The study was published online Thursday in the journal Lancet.

But there were few concrete numbers to rely on and researchers used modeling techniques to make their estimates.

“Even if it is not very solid data, we can say definitely that there are drug problems in most parts of the world,” said Theo Vos, the study’s senior author.