Biased under-reporting of research has been documented for well over two decades and the evidence for it is now overwhelming.1 2 3 4 Under-reporting is research misconduct and has serious consequences.5 6 It leads to overestimates of the benefits of treatments and underestimates of their harmful effects.7 Because of this it puts patients at risk and wastes healthcare resources.

Much of the criticism has focused on commercially funded trials, and justifiably so. There is clear and consistent evidence of under-reporting and manipulation of the scientific literature by the drug and devices industries,4 and industry sponsors most of the world’s clinical trials. But under-reporting is not confined to commercially sponsored trials. Indeed, early examples of failure to publish negative results came from academia.5 8

Nor has academia been any better than industry at cleaning up its act in the intervening decades. Because of trial registration, we can now estimate the magnitude and describe some of the characteristics of under-reporting of clinical trials. Only around half of all registered trials have published at least some of their results, and this level of under-reporting affects most types of trial: early and late phase, large and small, national and international, commercial and non-commercial (figure⇓). …