Association cannot be assumed to be causal

EDITOR,—The Royal College of Physicians has estimated that alcohol is responsible for 25 000 premature deaths every year.1 Medical professionals need to be cautious about making pronouncements that might encourage people to drink more. Two recent papers in the BMJ that seem to provide evidence of a protective effect of alcohol in relation to ischaemic heart disease2 3 were widely reported in the national media; it may be assumed that the net effect will be to shift upwards the distribution of alcohol …