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What's The Most Dangerous Drug In The World?


Robin Andrews

Science & Policy Writer

3882 What's The Most Dangerous Drug In The World?

Perception has a lot to do with it. Dennis Hill/Flickr (CC BY 2.0)

What is the most dangerous drug in the world? This sounds like a relatively simple question: Surely it’s the one most likely to kill you, right? As it turns out, it depends on a multitude of things, from the individual owner's risk to the wider risk to society – and perception plays a large part.

How Do You Define “Dangerous?”


David Nutt is the Edmond J. Safra professor of neuropsychopharmacology at Imperial College London. He’s one of the world’s foremost experts on drugs, in terms of their use, their effects on the human brain, and international drug policy. Drug Science – formally the Independent Scientific Committee on Drugs – is a science-led drugs charity and research organization headed by Professor Nutt.

In 2010, a now-infamous paper was published by the group detailing their scientific analysis on the harms of drugs available in the U.K., both legal and illegal. Sixteen parameters of harm were chosen, and were divided in terms of the specific drug’s direct and individual effects on the user. A direct effect of a drug on a person could be death through an overdose, for example; an indirect effect could be damage caused by becoming infected with HIV while using contaminated syringes. Each drug’s effect on others and the wider society were also taken into account.

The list included mortality likelihood, dependence, impairment of mental functioning, loss of tangible socioeconomic things (such as a house or a job), physical injury, and criminal activities. The economic cost to the country, as well as the international damage (in terms of political and societal destabilization, for example) were also considered.

“Ranking twenty different drugs on sixteen different harms – that’s the best method we’ve had,” Professor Nutt told IFLScience. In a more general sense, the detrimental effects of drugs could be divided into two broad categories: harm to others and harm to users.


This group also had to weight the different criteria – some harms were considered, albeit subjectively, more important than others. “There are two elements to it,” Nutt continued. “Deciding on the various harms – the 16 parameters – most experts agree on that. The more interesting question is how much you care about each of these different rankings; this is where the weightings come in. This could vary greatly depending on the group’s opinions.”

A European group also attempted the same process a few years after the publication of this Lancet study, in collaboration with Drug Science. In terms of the two groups, the British prioritized economic harm more, whereas the Europeans ranked personal harm as considerably more important.

One Every Ten Seconds

With all this taken into consideration, which drugs were considered the most harmful? Mostly due to its harm to others – including the wider economy – alcohol was considered to be by far the most dangerous. Heroin and crack cocaine were next on the list, mostly due to the harm to individual users, although they still had a significant “harm to others” component. Cannabis was ranked 8th for overall harm, whereas ecstasy and LSD were considered among the least harmful. Tobacco was ranked 6th, just behind cocaine.


Despite the European study using different harm weightings, the results were pretty much identical, with an extremely high level of agreement, or correlation, between the two studies. Only a few drugs – methamphetamine and ecstasy – changed positions slightly.

“We repeated the study at a European level, expanding it from a smaller British scale – and our experts really agree with each other,” lead author Dr. Jan van Amsterdam, of the Academic Medical Center at the University of Amsterdam, told IFLScience.

Regardless, the conclusion seems to be that alcohol is the most dangerous drug around. It directly causes a plethora of diseases, from cardiovascular and neurological disorders to liver degeneration; it indirectly causes transportation accidents, increases promiscuous activities and thus the likelihood of becoming infected by a range of pathogens, and makes an enormous dent in a nation’s economy as it pays for treatment for those suffering from alcohol-related problems.

The World Health Organization (WHO) estimates that 3.3 million deaths every year are caused by the harmful use of alcohol – that’s 5.9 percent of all annual deaths. Shockingly, this is roughly one person every 10 seconds.


A Matter of Perspective

Asking the question “what is the world’s most dangerous drug” is fraught with complex political and social history – and many people believe all illegal drugs to be far more dangerous than legal ones. The legal status of various drugs is somewhat arbitrary, defined long ago in many Western nations by quirks of history.

Heroin, for example, was regularly used in the U.K., prescribed by the National Health Service (NHS) to treat heroin addicts – small doses were used to wean people off it. “There were 1,000 addicts in 1971,” Nutt pointed out. “Then the government decided to get “hard on drugs”; by 1990, there were 200,000 addicts.

“Drugs policy is deliberately used as a political tool. The illegalizing of cannabis, for example, was driven by pressure from Egypt which insisted the UN add cannabis to the anti-drug conventions in order for its members to get access to military bases there.”


Cannabis is criminalized in most states in the U.S., but despite the scientific evidence suggesting it’s nowhere near as dangerous as alcohol, it’s costing up to $20 billion (£13 billion) per year to enforce its illegality. Legalizing it in the U.S., however, would earn the government billions in tax dollars, while taking the drug out of the hands of the criminal organizations that profit from it. By helping to fund the black market and associated crime, cannabis is far more dangerous as an illegal substance than it would be as a legal one.

Not All Drugs Were Created Equal

Governments often take a hard line on drugs in order to seem tough and, ultimately, more electable. It’s this attitude, exacerbated by the media, that encourages people to take an absolutist view: All drugs are extremely dangerous, and they must be stamped out at whatever cost. The scientific research, however, shows that not all drugs are created equal, and it’s the most widely available, easy to access drug of all that’s by far the most dangerous, by any measure.

If the danger of drugs is seen as a personal danger most of all – as the European study decided – then drug addiction problems should be treated more as a health issue, not as a policing issue. Alcoholism is treated as a health issue, and heroin addiction often isn’t – illegal substance abuse tends to be a criminal issue first and foremost. 


All drugs are dangerous to some degree. Clearly, the idea that a drug is more dangerous just because it’s illegal is completely unfounded.

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