In a scoping review, we have investigated the types of evidence that have been used to support 2421 pharmacovigilance signals communicated internationally.

Signals based only on anecdotal reports have become increasingly common and dominate the literature (70%).

Most signals based only on anecdotal reports are supported by evidence involving temporality and dechallenge/rechallenge, but clear reporting of how judgments of association or causality are made is uncommon (13%).