Internet discussions usually descend into abuse within a few postings. Whether this is because people these days are less polite and restrained than they used to be, or because the internet allows them to publish their first reactions without the time to cool off that older means of communication entailed, I do not know; but the fact is that those who take part in such discussions seem to confuse insult with argument and are seldom able to keep to the point for very long.

Doctors, if the internet discussions that follow articles that appear in the New England Journal of Medicine are anything to go by, are better than average. Often, indeed, though not always, they employ rational argument. Perhaps there is something to be said after all for a long and rigorous education.

Not long ago there appeared an article in the NEJM throwing doubt on the wisdom and even the ethics of screening by mammography for early cancer of the breast. A Swiss commission examined the evidence for the benefits and found none, or some so slight that it hardly counted. The best estimate they could come up with was that mammography saved one life from breast cancer per 1000 women aged 50 who underwent screening, but that the all-cause death rate in the screened and unscreened was practically the same. Not only did many screened women undergo unnecessary operations and much radiotherapy for false positive results, but those who offered the screening were little more honest than second-hand car salesmen, in effect preying on the women’s complete misunderstanding of the supposed benefits of screening. Women believe that even with screening they are twenty times more likely to die of the disease than in fact they are; and they overestimate the benefits of screening by eighty times.

In the circumstances, then, the Swiss panel suggested that screening by mammography should be stopped forthwith.