Safety and research
AE
Definition
An adverse event is an unfavourable medical occurrence observed during a study or use period, whether or not it is considered caused by the intervention.
Aliases and abbreviations
AE · undesirable medical occurrence · untoward medical occurrence
Editorial record
Published: August 25, 2026 · Reviewed: August 25, 2026
Expanded definition
An AE may be a symptom, sign, diagnosis, injury, laboratory abnormality, or other unfavourable occurrence that happens after participation or exposure begins.
The event is recorded because of timing and participant safety, not because causality has already been established. Investigators separately assess seriousness, severity, expectedness, and possible relationship to the intervention.
In stimulation studies, an expected sensory experience should be distinguished from an unwanted event, but the protocol must define how sensations, discomfort, skin findings, and medical events are collected and classified.
What the term does not establish
Why the distinction matters
Keeping occurrence, causality, severity, and seriousness separate prevents safety data from being exaggerated or dismissed.
Main guide
A focused overview of adverse-event reporting, tolerability, study populations, and product-specific boundaries.
Explore safety researchRelated terms
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Protocol and stimulation parameters
Editorial scope
This glossary entry supports general education. It does not diagnose, recommend treatment, or transfer findings from one VNS method, protocol, or device to another.