Around the world, politicians are working to ban e-cigarette marketing, limit their nicotine content, prohibit use in public buildings, and even to ban them entirely. There remains a need for policy makers to become better informed of the relative harms of nicotine delivery systems in order to build a regulatory framework that minimises harm. The aim of this study was to convene a group of experts with expertise in the field of nicotine and tobacco research from different disciplines (animal and behavioural pharmacology, toxicology, medicine, psychiatry, policy and law) that could discuss and agree on the harmfulness of nicotine-containing products, thus, providing a sound framework within which policy makers might work. An explanation of the MCDA process can be found in Drug Harms in the UK. The result was a striking ranking of these products in order of risk, based on scientific evidence and expertise.

Public Health England, a UK Government body, published a report on e-cigarettes attracting considerable press coverage. DrugScience's results formed the basis of their conclusions:

[DrugScience identified e-cigarettes] as having 4% of the relative harm of cigarettes overall (including social harm) and 5% of the harm to users ... In a nutshell, best estimates show e-cigarettes are 95% less harmful to your health than normal cigarettes, and when supported by a smoking cessation service, help most smokers to quit tobacco altogether.

E-cigarettes: an evidence update (Aug 2015)
Any way of radically reducing the death toll from tobacco would be a worldwide public health triumph to rival vaccination. This novel study shows that while quitting all nicotine products remains the healthiest option, switching down from an ultra high-risk product like cigarettes to a low risk product has a huge impact on harms. Nicotine products are therefore best understood as forming a steep gradient of risk, with cigarettes at the very top, and e-cigarettes quite close to the bottom. The key policy objective must be make it as easy as possible to descend from the summit, whilst limiting movement the other way.

Study lead author Professor David Nutt

Watch Prof. David Nutt talk about the MCDA technique for analysing drug and nicotine product harm

Graduate Institute Geneva, Nov 2014

What does it show?

The study showed that for all the fears expressed by politicians and journalists, electronic cigarettes pose only a shadow of the dangers of traditional cigarettes. Nicotine-containing products should not be lumped together as comparably harmful, as the products varied to a staggering extent, along a steep gradient. Cigarettes and small cigars are far more harmful than any of the other products. In comparison, products such as patches, gums and inhalers that deliver nicotine without a whole host of accompanying poisons are not completely free from harm, but, relative to smoked and chewed tobacco, the threat they pose to public health is near negligible. Electronic Nicotine Delivery Systems (such as e-cigarettes) were narrowly the most risky of this low-risk cluster, but the experts emphasise that they must be evaluated in terms of smokers moving to e-cigarettes rather than the small threat they may pose to non-smokers who take them up.

What are the limitations?

Many nicotine-containing cigarette-replacement products are relatively novel and consequently there exists limited data on harm – especially long-term harms. We acknowledge this is a limitation of these data and it is vital that this work is repeated as we learn more. In order to combat this, the group of experts worked face-to-face in a peer-review setting with impartial facilitation, sharing relevant data, knowledge and experience to ensure that all perspectives were heard. It is the combination of impartial facilitation, modelling (in this case, MCDA), and information technology (projecting the MCDA model for the group to observe as it was constructed and explored) that enables a group to outperform its members.