"Family, twin, and adoption studies also convincingly demonstrate a substantial genetic contribution to the development of addiction to nicotine, alcohol, and illicit drugs. Heritability estimates for nicotine, alcohol, and drug addiction are in the range of 50% to 60%." (1)
If this is so, then theoretically people could be genetically tested for their vulnerability to substance addiction and advised accordingly. And the others could continue in their habit, moderately reassured that they could stop if they so chose.
Testing might also help with more precise information about health risks. A longitudinal study of male British doctors (2) suggests that the average reduction in life expectancy is 10 years, but "that is not to say that all such smokers died about 10 years earlier than they would otherwise have done: some were not killed by their habit, but about half were, thereby losing on average more than 10 years of non-smoker life expectancy. Indeed, some of those killed by tobacco must have lost a few decades of life." It may be possible to identify the ones who are most at risk of dying in their middle years.
The same study also suggests that smoking for a few years may not be significantly life-threatening. For those in the 25-34 age group - where smoking prevalence is highest (3) - if they give up during this time, their life expectancy is almost exactly the same as for never-smokers:
|"Mortality in relation to smoking", etc. - Fig. 4 (selected area)|
Those who went ahead despite personalised warnings would at least be doing so on the basis of better information - and that then becomes a liberty issue, like hang-gliding (and cycling, the most dangerous form of transport).*
(1) "Genetic Vulnerability and Susceptibility to Substance Dependence" L.J. Bierut, US National Library of Medicine National Institutes of Health, February 2012 - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3095110/
(2) "Mortality in relation to smoking: 50 years' observations on male British doctors" Doll, Peto & Boreham, BMJ, May 2004 - http://www.bmj.com/content/328/7455/1519
(3) ASH "Facts at a glance", June 2016 - http://www.ash.org.uk/files/documents/ASH_93.pdf
*I was wrong, I'm afraid. Motorcycling is worse: 1,789 KSI (killed or seriously injured) per billion vehicle miles vs. 1,036 for pedal cycles. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/447674/pedal-cyclists-2013-data.pdf
I'm disappointed - I wanted something to get back at the Puritans of the road.