Nutt et al.'s experts have created a ranking system (out of 3) for a drug harmfulness hierarchy.
Topping the charts, heroin was classified as the most addictive drug, receiving a score of 2.5 out of a maximum score of 3. Heroin is an opiate that causes the level of dopamine in the brain’s reward system to increase by up to 200% in experimental animals. In addition to being arguably the most addictive drug, heroin is dangerous, too, because the lethal dose amount is only 5 times greater than the dose required for a high.
Heroin also has been rated as the second most harmful drug in terms of damage to both users and to society. The market for illegal opiates, including heroin, was estimated to be $68 billion worldwide in 2009.
Ranking at a close second, was alcohol. This legal drug was rated 2.2 out of 3. Alcohol has many effects on the brain, but in laboratory experiments on animals it increased dopamine levels in the brain’s reward system by 40-360% – and the more the animals drank the more dopamine levels increased.
The WHO has estimated that 2 billion people used alcohol in 2002 and more than 3 million people died in 2012 due to damage to the body caused by drinking. In addition, Alcohol has been ranked as the most damaging drug by other experts, too.
Rounding third would be crack cocaine. About 21% of people who try cocaine will become dependent on it at some time in their life, with powdered cocaine, which causes a milder high, following at fifth. Cocaine directly interferes with the brain’s use of dopamine to convey messages from one neuron to another. In essence, cocaine prevents neurons from turning the dopamine signal off, resulting in an abnormal activation of the brain’s reward pathways. In experiments on animals, cocaine caused dopamine levels to rise more than three times the normal level. It is estimated that between 14-20m people worldwide use cocaine and that in 2009 the cocaine market was worth about $75 billion.Cocaine is similar to other addictive stimulants, such as methamphetamine – which is becoming more of a problem as it becomes more widely available – and amphetamine.
Barbiturates – also known as blue bullets, gorillas, nembies, barbs and pink ladies – come in at number 4. This class of drugs were initially used to treat anxiety and to induce sleep. They interfere with chemical signaling in the brain, the effect of which is to shut down various brain regions. At low doses, barbiturates cause euphoria, but at higher doses they can be lethal because they suppress breathing. Barbiturate dependence was common when the drugs were easily available by prescription, but this has declined dramatically as other drugs have replaced them.
This presents an interesting claim in the role that availability plays in addiction. For instance, if an addictive drug is not widely available, it can do little harm.
This brings us to our next drug, Nicotine. The main addictive ingredient of tobacco. When somebody smokes a cigarette, nicotine is rapidly absorbed by the lungs and delivered to the brain. Although Nutt et al.'s expert panels rated nicotine as only the 12th most addictive substance, there are strong claims for its brute power in addiction.
Greater than two-thirds of Americans who tried smoking reported becoming dependent during their life. The WHO estimated there were more than 1 billion smokers and it has been estimated that tobacco will kill more than 8m people annually by 2030, gathered from their report in 2002.