If you are greatly afraid, however, such as being terrified that there is a burglar in your home that is about to harm you, the body produces a high degree stress response. We generally experience high degree stress responses as being anxiety attacks: where the changes are so profound they get our full attention. The greater the degree of anxiety and stress response, the more changes the body experiences.
The emotional effects of anxiety may include "feelings of apprehension or dread, trouble concentrating, feeling tense or jumpy, anticipating the worst, irritability, restlessness, watching (and waiting) for signs (and occurrences) of danger, and, feeling like your mind's gone blank" as well as "nightmares/bad dreams, obsessions about sensations, déjà vu, a trapped-in-your-mind feeling, and feeling like everything is scary."
Panic attacks are sudden periods of intense fear that may include palpitations, sweating, shaking, shortness of breath, numbness, or a feeling that something bad is going to happen. The maximum degree of symptoms occurs within minutes. Typically they last for about 30 minutes but the duration can vary from seconds to hours. There may be a fear of losing control or chest pain. Panic attacks themselves are not typically dangerous physically.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).