: excessive arousal: an abnormal state of increased responsiveness to stimuli that is marked by various physiological and psychological symptoms (such as increased levels of alertness and anxiety and elevated heart rate and respiration)
Although insomnia is considered a sleep disorder, its pathophysiology suggests hyperarousal during sleep and wakefulness. Daniel J. Buysse
To be given a diagnosis of PTSD, a person has to have been exposed to an extreme stressor or traumatic event to which he or she responded with fear, helplessness, or horror and to have three distinct types of symptoms consisting of reexperiencing of the event, avoidance of reminders of the event, and hyperarousal for at least one month. Rachel Yehuda