Tag Archives: Legislation

Permitted Blood Alcohol Level for Driving

In December 2014 the permitted blood alcohol concentration for drivers in Scotland was reduced from 0.08 g/dL to 0.05 g/dL. What effect do you think of this had on road traffic accidents?

Haghpanahan and colleagues performed a time-series analysis over the intervention period.[1] They adjusted for any underlying temporal trend and for season.  Road traffic accident data were obtained from police records and alcohol consumption from market research data. Automated traffic counters provided the denominators.

The legislation had absolutely no effect on the rate of road traffic accidents. Nor was it lower when compared to England and Wales where no reduction in permitted alcohol was made. In fact, the legislation had no effect on alcohol consumption.

Since a reduction in the permitted alcohol concentration can criminalise citizens, this study would suggest that reducing permitted alcohol concentrations over the range tested here, and without further measures, will do more harm than good.

— Richard Lilford, CLAHRC WM Director


  1. Haghpanahan H, Lewsey J, Mackay DF, McIntosh E, Pell J, Jones A, Fitzgerald N, Robinson M. An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment. Lancet. 2019; 393: 321-9.

Legalisation of Marijuana

Having borne down heavily on tobacco, it seems like everyone is now campaigning to make marijuana legal – are they mad?

A libertarian would say that there is no case to ban tobacco (or effectively ban it by draconian taxes on consumption). All tobacco can do is kill you, and as long as you know this you may use it. Marijuana is a different case altogether. It appears that it does not just kill you, it maims you – and not just your body, but you – your personality, your memory, your intelligence, i.e. your essence. And it is particularly attractive to teenagers – those with the most precious and vulnerable brains. Use is increasing in the US and has increased in association with decriminalisation, even if cause and effect is hard to prove.[1] Meanwhile a recent longitudinal cohort study found that persistent cannabis dependence was linked to downward socioeconomic mobility, financial difficulties, workplace problems, and relationship conflict.[2] It gets worse, the concentration of psycogenic compounds is increasing in the plant due to selective breeding. The attitude and fashion among liberal metropolitans “tobacco is vulgar, but marijuana is cool.” Have we gone mad? If we could confine the need to people over 18, and campaign against it, then over time we could reduce use. But a chemical that actually alters the structure of the adolescent brain and is more ubiquitous than boxing? We urgently need more information on the effects legalising cannabis has on usage. Also, more research on its effects on the brain using functional MRI. I wonder if Mendelian randomisation could shed light on causality?

— Richard Lilford, CLAHRC WM Director


  1. Azofeifa A, Mattson ME, Grant A. Monitoring Marijuana Use In the United States: Challenges in an Evolving Environment. JAMA. 2016; 316:1765-6.
  2. Cerdá M, Moffitt TE, Meier MH, et al. Persistent Cannabis Dependence and Alcohol Dependence Represent Risks for Midlife Economic and Social Problems: A Longitudinal Cohort Study. Clin Psychol Sci. 2016; 4(6): 1028-46.


Effect of Smoke-Free Legislation on Human Health

Two recent studies have considered the effect of smoke-free legislation bans on perinatal and child health. The first looks at smoke free legislation in England.[1] Their interrupted time series documents an immediate drop in stillbirths, low birth weight, and neonatal mortality following introduction of the legislation in July 2007. Interestingly, sudden infant death rates showed no change, perhaps because parents already avoided smoking at home?

The second paper is a systematic review of smoking bans in work places and/or public places, and at least one measure of health.[2] Eleven studies were identified, all interrupted time series. Again smoke free bans were associated with reductions in pre-term birth and hospital attendance for asthma, but this time no effect on birth weight was noted. The CLAHRC WM Director fancies himself as a libertarian. The limit on personal liberty is maternal risk of physical harm to others. He therefore supports smoke-free legislation.

— Richard Lilford, CLAHRC WM Director


  1. Been JV, Mackay DF, Millett C, Pell JP, van Schayck OCP, Sheikh A. Impact of smoke-free legislation on perinatal and infant mortality: a national quasi-experimental study. Sci Rep. 2015;5:13020.
  2. Been JV, Nurmatov UB, Cox B, Nawrot TS, von Schayck CP, Sheikh A. Effect of smoke-free legislation on perinatal and child health: a systematic review and meta-analysis. Lancet. 2014;383:1549-600.