Some research suggests that your body's natural fight-or-flight response to danger is involved in panic attacks. For example, if a grizzly bear came after you, your body would react instinctively. Your heart rate and breathing would speed up as your body prepared for a life-threatening situation. Many of the same reactions occur in a panic attack. But it's unknown why a panic attack occurs when there's no obvious danger present.
There are two very important guidelines to think about, aside from symptoms. These are duration of symptoms and level of impairment. Anxiety is a normal reaction to stressful situations, and even high levels of anxiety can be healthy and beneficial at times. Disorders are only present when anxiety symptoms last for several weeks to months and significantly interfere with every day function or cause long-lasting distress.
Occasional anxiety is an expected part of life. You might feel anxious when faced with a problem at work, before taking a test, or before making an important decision. But anxiety disorders involve more than temporary worry or fear. For a person with an anxiety disorder, the anxiety does not go away and can get worse over time. The symptoms can interfere with daily activities such as job performance, school work, and relationships.