adverse event

https://doi.org/10.1351/goldbook.15448
Occurrence that causes an adverse effect.
Note: An adverse event in clinical studies is any untoward reaction in a human subject participating in a research project; such an adverse event, which may be a psychological reaction, must be reported to an institutional review board.
Source:
PAC, 2007, 79, 1153. (Glossary of terms used in toxicology, 2nd edition (IUPAC Recommendations 2007)) on page 1162 [Terms] [Paper]