Thursday September 4 2014
E-cigarettes have gone from niche product to big business
“E-cigarettes could lead to using cocaine and cannabis scientists say,” the Daily Mirror reports.
In an article sure to prove controversial, two neuroscientists argue that nicotine may "prime" the brain to become addicted to harder drugs, such as cocaine.
The story comes from an article that argues that nicotine alters the brain’s circuitry, lowering the threshold for addiction to other substances such as cannabis and cocaine. Electronic cigarettes, the authors point out, are “pure nicotine delivery devices”, which could increase drug addiction among young people.
The “gateway drug” hypothesis is that use of certain (usually legal) drugs such as nicotine and alcohol can lead to the use of hard illegal drugs such as cocaine. This article argues that nicotine is such a drug and includes previous research by the authors that tested this hypothesis in a mouse model.
The authors’ argument is based on the assumption that e-cigarette (or other nicotine) users will go on to use drugs such as cocaine. This assumption is unproven. While it is true that most cocaine users are also smokers, this does not equate to stating that most smokers use cocaine.
The article is of interest but it does not prove that e-cigarettes are a “gateway” to the use of drugs such as cocaine.
Where did the story come from?
The article is the print version of a lecture given by two researchers from Columbia University in the US. Their previous work in this area has been funded by the Howard Hughes Medical Institute, the National Institutes of Health and the National Institute on Drug Abuse, all in the US. One of the researchers, Professor Eric Kandel, shared the 2000 Nobel Prize in Physiology or Medicine for his discoveries related to the molecular basis of memory.
The article was published in the peer-reviewed New England Journal of Medicine on an open access basis so it is free to read online.
Coverage in the UK media was accurate but uncritical.
What kind of research was this?
This was not research but an article, based on a lecture, that presented evidence in favour of the theory that nicotine “primes” the brain for the use of other drugs such as cannabis and cocaine.
The authors say that while studies have shown that nicotine use is a gateway to the use of cannabis and cocaine in human populations, it has not been clear how nicotine accomplishes this. They say they have brought “the techniques of molecular biology” to bear on the question, revealing the action of nicotine in the brains of mice.
What did the article involve?
The authors first explain the gateway hypothesis (developed previously by one of them), which argues that in western societies, there is a “well defined” developmental sequence of drug use that starts with a legal drug and proceeds to illegal drugs. Specifically, it says, the use of alcohol and tobacco precede the use of cannabis, which in turn precedes the use of cocaine and other illicit drugs. They then review their own studies in which they tested the gateway hypothesis in a mouse model.
Using this model they examined both addictive behaviour, brain “plasticity” (changes to the structures of the brain) and activity of a specific gene associated with addiction, in various experiments in which mice were exposed to both nicotine and cocaine.
One of the behavioural experiments they report on, for example, shows that mice given nicotine for seven days, followed by four days of nicotine and cocaine, were significantly (98%) more active than controls.
They also say they found that exposing mice brains to nicotine appeared to increase the “rewarding” properties of cocaine by encouraging production of the neurotransmitter dopamine.
Other experiments they report on found that nicotine given to mice before cocaine increased the expression of a gene that magnifies the effect of cocaine.
This “priming” effect, they say, does not occur unless nicotine is given repeatedly and in close conjunction with cocaine.
They then report on studies that they say show that nicotine also primes human brains to respond to cocaine, with the rate of cocaine dependence highest among users who started using cocaine after having smoked cigarettes.
Their conclusion is that, in humans, nicotine affects the circuitry of the brain in a manner that enhances the effects of a subsequent drug and that this “priming effect” happens if cocaine is used while using nicotine.
This effect is likely to occur, they argue, whether the exposure is from tobacco smoking, passive smoking or e-cigarettes.
They also argue that e-cigarettes are increasingly used by adolescents and young adults, with the potential for creating a new generation of people addicted to nicotine. “Whether e-cigarettes will prove to be a gateway to the use of combustible cigarettes and illicit drugs is uncertain but it is clearly a possibility.”
The article is of interest but it does not prove that e-cigarettes are a “gateway” to the use of drugs such as cocaine. The authors present evidence, much of it from their own research, in support of this hypothesis, but it remains just that – a hypothesis.
You could also make the point that it is somewhat unfair to demonise e-cigarettes in this way. Any product containing nicotine, such as patches or gum, could also be classed as a “gateway drug”, but as they release nicotine slowly these are not thought to be as “addictive”.
Also, as the authors point out, the “gateway drug” hypothesis is not universally accepted by addiction specialists. There is another hypothesis that the use of multiple drugs reflects a general tendency to drug use and that it is this tendency to addiction, rather than the use of a particular drug, that increases the risk of progressing to another drug.
From 2016 e-cigarettes are likely to be classed as "medicines", which means they will face stringent checks by medicine regulator the MHRA, and doctors will be able to prescribe them to smokers to help them cut down or quit. Tighter regulation will ensure the products are safe and effective.
If you want to try a safer alternative to cigarettes but are concerned about the uncertainties surrounding e-cigarettes, you may wish to consider a nicotine inhalator. This licensed quit smoking aid, available on the NHS, consists of just a mouthpiece and a plastic cartridge. It’s proven to be safe, but the nicotine vapour only reaches the mouth rather than the lungs, so you don’t get the quick hit of nicotine that comes with e-cigarettes.
It is well known that nicotine is addictive. Despite the risk of addiction and other uncertainties, e-cigarettes are likely to be safer than cigarettes (or other tobacco products). There is no conclusive evidence that using e-cigarettes will increase your risk of developing a drug addiction.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.