EVEN negative findings tell a story – but when experimental drugs are tested in animals, negative results are far less likely to be reported than positive ones.

This makes drugs appear more effective than they really are. As a result, expensive clinical trials can sometimes go ahead when they are unlikely to succeed, diverting resources from better options, says Malcolm Macleod of the University of Edinburgh, UK.

When Macleod’s team analysed 16 reviews covering 525 published papers on animal tests of potential stroke treatments, they found that only 10 papers, or 2 per cent, reported that a treatment failed. Combining this with their own experiences as researchers, …