There are several different anxiety-related disorders. Some symptoms overlap across many of these disorders, and others are more specific to a single disorder. In general, however, all anxiety-related disorders feature worry, nervousness, or fear that is ongoing, excessive, and has negative effects on a person's ability to function. It can be tricky to decide when anxiety is typical or linked to a disorder, which is why diagnoses should be made by licensed professionals, such as psychologists or psychiatrists.
What happens, exactly? "We all physically respond to stress," says Barbara O. Rothbaum, PhD, psychiatry professor and director, Trauma and Anxiety Recovery Program, at Atlanta's Emory University School of Medicine. "You might feel anxious about work-related problems, taking a big exam, or making an important decision. But someone who suffers from panic disorder may react to those same moderate pressures with an exaggerated physical reaction-as if he or she were about to be attacked by a wild tiger or fall from a great height. It's full-on, adrenaline-pumping, fight-or-flight response."

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).