For many of us, the move towards an evidence based approach to medicine has largely been a welcome one. We have learnt to evaluate therapies rigorously and be highly sceptical of expert enthusiasm for them. Perhaps most importantly, we now try to turn routinely to summaries of the evidence rather than rely on single studies. For what we assumed were good reasons, systematic reviews and meta-analyses have become gold standards, whether we are a politician, a physician, or simply a citizen. But is it fool’s gold? In our collective zeal to summarise, we have too often ignored the fact that a vast and growing proportion of those original studies are industry sponsored, which means that they tend to exaggerate benefits and play down harms. Summarising that bias doesn’t make it go away. Medicine’s prized evidence base has become debased.

An international team of researchers from across Europe and North America recently examined 29 meta-analyses published in leading medical journals.1 Those meta-analyses summarised results of more than 500 trials of top selling drugs for conditions …