Hypervigilance

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.^[1][2] Hypervigilance can be a symptom of posttraumatic stress disorder^[3] 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.

  

Symptoms

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 'over-react' to loud & unexpected noises; become agitated in highly crowded or noisy environments etc. They will often have a difficult time getting to sleep or staying asleep.^[4]

http://en.wikipedia.org/wiki/Hypervigilance