[1] When reflecting human emotion and behavior, it is commonly defined as the tendency to react to stimuli with negative affective states (especially anger) and temper outbursts, which can be aggressive.
Distressing or impairing irritability is important from a mental health perspective as a common symptom of concern and predictor of clinical outcomes.
[3] It is commonly defined as the tendency to react to stimuli with the experience of negative affective states (especially anger) and temper outbursts, which may or may not be aggressive.
As an emotional and behavioral symptom in humans, someone is considered to be irritable when they have a short temper, become easily frustrated, or feel grouchy or grumpy.
[6] Finally, it is a notable characteristic of delirium, dementia, hormonal change, metabolic disturbance, chronic stress, pain, and substance/medication withdrawal.
If a person presents as uncharacteristically irritable, then a clinician may become concerned a change or episodic illness, such as a neurologic insult or mood disorder.