Hypervigilance is characterized by increased sensory response together with exaggerated intensity of behavior, combining to exhibit greatly increased response to perceived threats. It is usually accompanied with increased anxiety which can lead to fatigue and exhaustion. The patient will constantly be scanning the environment with all five of the main senses to respond to anything in the environment. It can lead to obsessive behavior patterns, an inability to interact socially, and a breakdown of relationships. It often makes sleep difficult or impossible.
Care must be taken to distinguish hypervigilance from paranoia. In the latter, the patient is reacting to imagined threats, while in the former, the patient reacts to real stimuli that they perceive to be threatening or stimuli that triggers memories of previous trauma.
It can also be distinguished from hyperaroused states, such as those which occur with stimulants. With hypervigilance, the patient will still respond to their surroundings and interact with other people, although with difficulty. Hypervigilance at Wikipedia