Causes of Panic disorder


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Cause details for Panic disorder: Studies in animals and humans have focused on pinpointing the specific brain areas and circuits involved in anxiety and fear, which underlie anxiety disorders such as panic disorder. Fear, an emotion that evolved to deal with danger, causes an automatic, rapid protective response that occurs without the need for conscious thought. It has been found that the body's fear response is coordinated by a small structure deep inside the brain, called the amygdala.

The amygdala, although relatively small, is a very complicated structure, and recent research suggests that anxiety disorders may be associated with abnormal activitation in the amygdala. One aim of research is to use such basic scientific knowledge to develop new therapies. 1

is a description of some of the most important new research on panic disorder and its causes.

Genetics.   Panic disorder runs in families. One study has shown that if one twin in a genetically identical pair has panic disorder, it is likely that the other twin will also. Fraternal, or non-identical twin pairs do not show this high degree of "concordance" with respect to panic disorder. Thus, it appears that some genetic factor, in combination with environment, may be responsible for vulnerability to this condition.

NIMH-supported scientists are studying families in which several individuals have panic disorder. The aim of these studies is to identify the specific gene or genes involved in the condition. Identification of these genes may lead to new approaches for diagnosing and treating panic disorder.

Brain and Biochemical Abnormalities.   One line of evidence suggests that panic disorder may be associated with increased activity in the hippocampus and locus coeruleus, portions of the brain that monitor external and internal stimuli and control the brain's responses to them. Also, it has been shown that panic disorder patients have increased activity in a portion of the nervous system called the adrenergic system, which regulates such physiological functions as heart rate and body temperature. However, it is not clear whether these increases reflect the anxiety symptoms or whether they cause them.

Another group of studies suggests that people with panic disorder may have abnormalities in their benzodiazepine receptors, brain components that react with anxiety-reducing substances within the brain.

In conducting their research, scientists can use several different techniques to provoke panic attacks in people who have panic disorder. The best known method is intravenous administration of sodium lactate, the same chemical that normally builds up in the muscles during heavy exercise. Other substances that can trigger panic attacks in susceptible people include caffeine (generally 5 or more cups of coffee are required). Hyperventilation and breathing air with a higher-than-usual level of carbon dioxide can also trigger panic attacks in people with panic disorder.

Because these provocations generally do not trigger panic attacks in people who do not have panic disorder, scientists have inferred that individuals who have panic disorder are biologically different in some way from people who do not. However, it is also true that when the people prone to panic attacks are told in advance about the sensations these provocations will cause, they are much less likely to panic. This suggests that there is a strong psychological component, as well as a biological one, to panic disorder.

NIMH-supported investigators are examining specific parts of the brain and central nervous system to learn which ones play a role in panic disorder, and how they may interact to give rise to this condition. Other studies funded by the Institute are under way to determine what happens during "provoked" panic attacks, and to investigate the role of breathing irregularities in anxiety and panic attacks.

Animal Studies.   Studies of anxiety in animals are providing NIMH-sponsored researchers with clues to the underlying causes of this phenomenon. One series of studies involves an inbred line of pointer dogs that exhibit extreme, abnormal fearfulness when approached by humans or startled by loud noises. In contrast with normal pointers, these nervous dogs have been found to react more strongly to caffeine and to have brain tissue that is richer in receptors for adenosine, a naturally occurring sedative that normally exerts a calming effect within the brain. Further study of these animals is expected to reveal how a genetic predisposition toward anxiety is expressed in the brain.

Other animal studies involve macaque monkeys. Some of these animals exhibit anxiety when challenged with an infusion of lactate, much like people with panic disorder. Other macaques do not exhibit this response. NIMH-supported scientists are attempting to determine how the brains of the responsive and non-responsive monkeys differ. This research should provide additional information on the causes of panic disorder.

In addition, research with rats is exploring the effect of various medications on the parts of the brain involved in anxiety. The aim is to develop a clearer picture of which components of the brain are responsible for anxiety, and to learn how their actions can be brought under better control.

Cognitive Factors.   Scientists funded by NIMH are investigating the basic thought processes and emotions that come into play during a panic attack and those that contribute to the development and persistence of agoraphobia. The Institute also supports research evaluating the impact of various versions of cognitive-behavioral therapy to determine which variants of the procedure are effective for which people. The NIMH panic disorder research program will also explore the effects of interpersonal stress such as marital conflict on panic disorder with agoraphobia and determine if including spouses in the cognitive-behavioral treatment of the condition improves outcome.2

Triggers discussion for Panic disorder: Initial panic attacks may occur when people are under considerable stress, from an overload of work, for example, or from the loss of a family member or close friend. The attacks may also follow surgery, a serious accident, illness, or childbirth. Excessive consumption of caffeine or use of cocaine or other stimulant drugs or medicines, such as the stimulants used in treating asthma, can also trigger panic attacks. 2

Related information for causes of Panic disorder: Further relevant information on causes of Panic disorder may be found in the risk factors for Panic disorder and underlying causes of Panic disorder.

Footnotes:
1. excerpt from Facts about Panic Disorder: NIMH
2. excerpt from Understanding Panic Disorder: NIMH

Last revision: July 1, 2003

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