What are the most addictive drugs?
This question seems simple, but the answer depends on whom you ask.
From the points of view different researchers, the potential for a drug to be addictive can be judged in terms of the harm it causes, the street value of the drug, the extent to which the drug activates the brain’s dopamine system, how pleasurable people report the drug to be, the degree to which the drug causes withdrawal symptoms, and how easily a person trying the drug will become hooked.
There are other facets to measuring the addictive potential of a drug, too, and there are even researchers who argue that no drug is always addictive.
Given the varied view of researchers, then, one way of ranking addictive drugs is to ask expert panels. In 2007, David Nutt and his colleagues asked addiction experts to do exactly that – with some interesting findings.
Nutt et al.’s experts ranked heroin as the most addictive drug, giving it 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 dose that can cause death is only five 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.
Although legal in the US and UK, alcohol was rated as the second most addictive substance by Nutt et al.’s experts (scoring 2.2 out of a maximum 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.
Some 22% of people who have taken a drink will develop dependence on alcohol at some point during their life. The WHO has estimated that 2 billion people used alcohol in 2002 and more than 3m people died in 2012 due to damage to the body caused by drinking. Alcohol has been ranked as the most damaging drug by other experts, too.
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.
Crack cocaine has been ranked by experts as being the third most damaging drug and powdered cocaine, which causes a milder high, as the fifth most damaging. About 21% of people who try cocaine will become dependent on it at sometime in their life. 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.
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