A new study published in The Lancet reveals that heroin accounted for more than half of the 78,000 deaths from illegal drugs in 2010, but amphetamine had most addicts.
In a wide-ranging probe into the health impacts from four illicit drugs, a team led by Louisa Degenhardt at Australia's University of New South Wales also found that two-thirds of addicts are men, with the biggest problems emerging in males aged 20 to 29.
More than 55 percent of drug-related deaths in 2010 were caused by opioids, the category which is dominated by heroin, according to their probe.
Adding to the dependence risk from heroin is the peril from injecting drug use, for shared syringes help spread HIV and hepatitis.
The study, based on a new analysis of the vast Global Burden of Disease Study for 2010, predictably found that cannabis was the most-used illegal drug worldwide.
Like cocaine, it was a smaller source of death and disease compared to heroin and amphetamines, the investigation found.
As for drug addiction, the paper found that 17.2 million people were dependent on amphetamines in 2010, compared to 15.5 million for opioids and 13 million for cannabis.
A regional breakdown of the figures found that rich economies such as the United States, Britain and Australia had 20 times the rate of death and disease compared with the least affected countries. Among developing economies, South Africa stood out as having exceptionally high rates.
Cocaine dependence was highest in North America and Latin America, and Australasia and Western Europe had some of the high rates of heroin dependence, it found.
"Our results clearly show that illicit drug use is an important contributor to the global disease burden," said Degenhardt.
"Although we have fewer means of responding to some causes of burden, such as cocaine and amphetamine dependence, well-evaluated and effective interventions can substantially reduce two major causes of burden," she said, pointing to addiction to opioids and injecting drug use.
But, added Degenhardt, "the challenge will be to deliver these efficiently and on a scale needed to have an effect on a population level."
Using high-powered computer modelling, the team estimated that disability and illness caused by the four categories of drugs rose by more than half between 1990 and 2010, a rise partly explained by population growth but also by heroin addiction.
Overall, illicit drug dependence amounted in 2010 to just under one percent of the total global burden of death and illness.
This is only one-tenth of that inflicted by dependence on alcohol and tobacco, which however occurs among far more people.
Ecstasy and LSD were not included in the study, as the data for use of these drugs was often sketchy.