The Difference between Adverse Events and Negative Side Effects

By: Marielise Torres, iRACE FSUIntern

At the IRACE lab, we throw around many terms that are used for different purposes whether that be describing new research findings or coming up with new topics to discuss and question. But do you know the difference between Adverse Events and Side Effects?

Adverse Events include any unexpected medical event that is generally harmful to the participant. Depending on whether the event is distinguished as serious or not, the effects of the event can cause complications or possibly become life-threatening. They include the whole scope of negative outcomes of both medical and research practices. But not all adverse events are negative, for example, an adverse event includes the effect that Viagra has on erectile dysfunction as its purpose was heart medication during its development.

Negative Side Effects include a secondary undesirable but expected addition to a treatment or medication. Side effects are generally known effects other than that are intended due to their usual mild and self-resolving nature. For example, a Side effect of aspirin (blood-thinning medication) includes nose bleeds and causes you to bruise easily.

Even though adverse events encapsulate negative side effects there are some differences between their terminology and use in both the field of medicine and in research. Adverse events may include side effects, but side effects do not include adverse events. Adverse events include the unexpected inherently negative side effects or outcomes of practices that are not only from a procedure but can also be concluded from human error. Side effects, on the other hand, include an undesirable secondary effect to a treatment or medication. Most of the time the term adverse event is used during research trials discussing the use of a new medication or treatment option, while side effects are used for most to all medications and treatments provided today. The term side effect is usually used more informally and throughout normal conversation. Adverse events usually contain a more formal connotation which is why it is discussed in more research formats. For a patient or research participant, knowing the difference between these subjects may not be of major importance, but having a clear understanding of the differences between the two can help you prepare for a doctor's visit or participation in research.