On 2015 Apr 02, Marcus Munafò commented:

Carter and colleagues [1] report that 17% of the excess mortality among smokers is due to causes to yet established. This is an important insight – we know that smoking kills, but do not fully understand how. Nevertheless, there are reasons for being cautious about ascribing a direct causal role to smoking for some of the outcomes reported. The supplementary appendix indicates substantial excess mortality among smokers for “all other mental diseases”, including suicide. However, homicide is related to smoking in a similar way to suicide [2], which casts doubt on the possibility that smoking may be acting via a biological pathway. Mendelian randomization [3] offers a possible solution, protecting against confounding and reverse causality and enabling stronger causal inference. Since we do not yet fully understand why smoking kills, we have established the Causal Analyses for Research on Tobacco and Alcohol (CARTA) consortium to use Mendelian randomization to elucidate the causal role of smoking on a range of health outcomes and intermediate markers (http://www.bris.ac.uk/expsych/research/brain/targ/research/collaborations/carta/), which has failed to provide evidence that smoking causes depression [4].

Marcus Munafò, Amy Taylor and George Davey Smith

1. Carter, B.D., et al., Smoking and mortality--beyond established causes. N Engl J Med, 2015. 372(7): p. 631-40.
2. Davey Smith, G., A.N. Phillips, and J.D. Neaton, Smoking as "independent" risk factor for suicide: illustration of an artifact from observational epidemiology? Lancet, 1992. 340(8821): p. 709-12.
3. Davey Smith, G. and S. Ebrahim, 'Mendelian randomization': can genetic epidemiology contribute to understanding environmental determinants of disease? Int J Epidemiol, 2003. 32(1): p. 1-22.
4. Taylor, A.E., et al., Investigating the possible causal association of smoking with depression and anxiety using Mendelian randomisation meta-analysis: the CARTA consortium. BMJ Open, 2014. 4(10): p. e006141.

On 2015 Apr 02, Marcus Munafò commented:

Carter and colleagues [1] report that 17% of the excess mortality among smokers is due to causes to yet established. This is an important insight – we know that smoking kills, but do not fully understand how. Nevertheless, there are reasons for being cautious about ascribing a direct causal role to smoking for some of the outcomes reported. The supplementary appendix indicates substantial excess mortality among smokers for “all other mental diseases”, including suicide. However, homicide is related to smoking in a similar way to suicide [2], which casts doubt on the possibility that smoking may be acting via a biological pathway. Mendelian randomization [3] offers a possible solution, protecting against confounding and reverse causality and enabling stronger causal inference. Since we do not yet fully understand why smoking kills, we have established the Causal Analyses for Research on Tobacco and Alcohol (CARTA) consortium to use Mendelian randomization to elucidate the causal role of smoking on a range of health outcomes and intermediate markers (http://www.bris.ac.uk/expsych/research/brain/targ/research/collaborations/carta/), which has failed to provide evidence that smoking causes depression [4].

Marcus Munafò, Amy Taylor and George Davey Smith

1. Carter, B.D., et al., Smoking and mortality--beyond established causes. N Engl J Med, 2015. 372(7): p. 631-40.
2. Davey Smith, G., A.N. Phillips, and J.D. Neaton, Smoking as "independent" risk factor for suicide: illustration of an artifact from observational epidemiology? Lancet, 1992. 340(8821): p. 709-12.
3. Davey Smith, G. and S. Ebrahim, 'Mendelian randomization': can genetic epidemiology contribute to understanding environmental determinants of disease? Int J Epidemiol, 2003. 32(1): p. 1-22.
4. Taylor, A.E., et al., Investigating the possible causal association of smoking with depression and anxiety using Mendelian randomisation meta-analysis: the CARTA consortium. BMJ Open, 2014. 4(10): p. e006141.