Evidence quality
Adverse event
An unwanted health event occurring during a study or treatment period.
What it means
Definition
Adverse event: An adverse event is not always caused by the intervention, but it needs tracking and comparison between groups to understand possible harms.
What it can tell you
It can help clarify what sort of evidence or claim is being discussed.
What it cannot tell you
It cannot, by itself, prove that the headline is accurate or clinically important.
Headline trap
Why this matters in headlines
A trial should report adverse events as well as benefits, especially for preventive treatments used by healthy people.