In the central nervous system (CNS), the major mediators of the symptoms of anxiety disorders appear to be norepinephrine, serotonin, dopamine, and gamma-aminobutyric acid (GABA). Other neurotransmitters and peptides, such as corticotropin-releasing factor, may be involved. Peripherally, the autonomic nervous system, especially the sympathetic nervous system, mediates many of the symptoms. Increased flow in the right parahippocampal region and reduced serotonin type 1A receptor binding in the anterior and posterior cingulate and raphe of patients are the diagnostic factors for prevalence of anxiety disorder.
Warren: So if you’re walking down a dark alley, you are probably thinking that there could be potential danger; that anxiety of anticipation, the feeling in your stomach, the elevated heart rate. But if you’re walking down that alley and somebody jumps out with a knife, then you’re likely to have a panic attack — an overwhelming urge to escape a situation that is dangerous.
The review, conducted by researchers at Cambridge University in England, also found that people with chronic health conditions were more likely to experience anxiety. According to the review, almost 11 percent of people with heart disease in Western countries reported having generalized anxiety disorder (GAD). In addition, 32 percent of those with multiple sclerosis had some kind of anxiety disorder. (3)

Some of these symptoms will most likely be present in a panic attack. The attacks can be so disabling that the person is unable to express to others what is happening to them. A doctor might also note various signs of panic: The person may appear to be very afraid or shaky or be hyperventilating (deep, rapid breathing that causes dizziness). Anxiety attacks that take place while sleeping, also called nocturnal panic attacks, occur less often than do panic attacks during the daytime, but affect a large percentage of people who suffer from daytime panic attacks. Individuals with nocturnal panic attacks tend to have more respiratory symptoms associated with panic and have more symptoms of depression and of other psychiatric disorders compared to people who do not have panic attacks at night. Nocturnal panic attacks tend to result in sufferers waking suddenly from sleep in a state of sudden fright or dread for no known reason. As opposed to people with sleep apnea and other sleep disorders, sufferers of nocturnal panic can have all the other symptoms of a panic attack. Although nocturnal panic attacks usually last no more than 10 minutes, it can take much longer for the person to fully recover from the episode.
Although many people breathe into a paper bag in an attempt to alleviate the hyperventilation that can be associated with panic, the benefit received may be the result of the individual thinking it will help (a placebo effect). Unfortunately, breathing into a paper bag while having trouble breathing can worsen symptoms when the hyperventilation is caused by a condition associated with oxygen deprivation, like an asthma attack or a heart attack.

It is not clear what causes panic disorder. In many people who have the biological vulnerability to panic attacks, they may develop in association with major life changes (such as getting married, having a child, starting a first job, etc.) and major lifestyle stressors. There is also some evidence that suggests that the tendency to develop panic disorder may run in families. People who suffer from panic disorder are also more likely than others to suffer from depression, attempt suicide, or to abuse alcohol or drugs.
At some point in our lives, most of us will experience a panic attack in response to an actual danger or acute stress. But when panic attacks occur or recur for no reason and in the absence of danger or extreme stress, or when the fear of experiencing another attack is so strong that you change your behavior by avoiding certain places or people, you may have panic disorder.
Social anxiety disorder (previously called social phobia): People with social anxiety disorder have a general intense fear of, or anxiety toward, social or performance situations. They worry that actions or behaviors associated with their anxiety will be negatively evaluated by others, leading them to feel embarrassed. This worry often causes people with social anxiety to avoid social situations. Social anxiety disorder can manifest in a range of situations, such as within the workplace or the school environment.
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