Brain and Biochemical Abnormalities

One line of evidence suggests that panic disorder may be associated with increased activity in the hippocampus and locus ceruleus, 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.

FINDING HELP FOR PANIC DISORDER

Often the person with panic disorder must undertake a strenuous search to find a therapist who is familiar with the most effective treatments for the condition. A list of places to start follows. The Anxiety Disorders Association of America can provide a list of professionals in your area who specialize in the treatment of panic disorder and other anxiety disorders.

Self-help and support groups are the least expensive approach to managing panic disorder, and are helpful for some people. A group of about 5 to 10 people meet weekly and share their experiences, encouraging each other to venture into feared situations and cope effectively with panic attacks. Group members are in charge of the sessions. Often family members are invited to attend these groups, and at times a therapist or other panic disorder expert may be brought in to share insights with group members. Information on self-help groups in specific areas of the country can be obtained from the Anxiety Disorders Association of America.

Sources of Referral to Professional Help for Panic Disorder

Here are the types of people and places that will make a referral to, or provide, diagnostic and treatment services for a person with symptoms resembling those described in this brochure. Also check the Yellow Pages under "mental health," "health," "anxiety," "suicide prevention," "hospitals," "physicians," "psychiatrists," "psychologists," or "social workers" for phone numbers and addresses.

• Family doctors
• Mental health specialists, such as psychiatrists, psychologists, social workers, or mental health counselors
• Health maintenance organizations
• Community mental health centers
• Hospital psychiatry departments and outpatient clinics
• University- or medical school-affiliated programs and clinics
• State hospital outpatient clinics
• Family service/social agencies
• Private clinics and facilities
• Employee assistance programs
• Local medical, psychiatric, or psychological societies