Hypervigilance is an enhanced state of sensory sensitivity accompanied by an exaggerated intensity of behaviors whose purpose is to detect threats. Hypervigilance is also accompanied by a state of increased anxiety which can cause exhaustion. Other symptoms include: abnormally increased arousal, a high responsiveness to stimuli, and a constant scanning of the environment for threats.
In hypervigilance, there is a perpetual scanning of the environment to search for sights, sounds, people, behaviors, smells, or anything else that is reminiscent of threat or trauma. The individual is placed on high alert in order to be certain danger is not near. Hypervigilance can lead to a variety of obsessive behavior patterns, as well as producing difficulties with social interaction and relationships.
Hypervigilance can be a symptom of post traumatic stress disorder (PTSD) and various types of anxiety disorder. It is distinguished from paranoia. Paranoid states, such as those in schizophrenia, can seem superficially similar, but are characteristically different.
Hypervigilance is differentiated from dysphoric hyperarousal in that the person remains cogent and aware of his or her surroundings. In dysphoric hyperarousal, the PTSD victim may lose contact with reality and re-experience the traumatic event verbatim. Where there have been multiple traumas, a person may become hypervigilant and suffer severe anxiety attacks intense enough to induce a delusional state where the effect of the traumas overlap: e.g., one remembered firefight may seem too much like another for the person to maintain calm. This can result in the thousand-yard stare.
People suffering from hypervigilance may become preoccupied with studying their environment for possible threats, causing them to lose connections with their family and friends. They will 'overreact' to loud and unexpected noises or become agitated in highly crowded or noisy environments. They will often have a difficult time getting to sleep or staying asleep.