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Anxiety disorders - Causes

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of anxiety.

Alternative Names

Obsessive-compulsive disorder; Panic disorder; Phobias; Post-traumatic stress disorder

Causes:

A person's genetics, biochemistry, environment, history, and psychological profile can all contribute to the development of anxiety disorders. Most people with these disorders seem to have a biological vulnerability to stress, making them more susceptible to environmental stimuli than the rest of the population.

Biochemical Factors

Studies suggest that an imbalance of certain substances called neurotransmitters (chemical messengers in the brain) may contribute to anxiety disorders. The neurotransmitters targeted in anxiety disorders are gamma-aminobutyric acid (GABA), serotonin, dopamine, and epinephrine. Serotonin appears to be specifically important in feelings of well-being, and deficiencies are highly related to anxiety and depression. Stress hormones such as cortisol also play a role.

Brain Structure Factors

Studies using imaging techniques, particularly magnetic resonance imaging (MRI), have helped to identify different areas of the brain associated with anxiety responses.

An MRI (magnetic resonance imaging) of the brain creates a detailed image of the complex structures in the brain. An MRI can give a three-dimensional depiction of the brain, making location of problems such as tumors or aneurysms more precise.

In particular, research has focused on changes in the amygdala, which is sometimes referred to as the "fear center." This part of the brain regulates fear, memory, and emotion and coordinates these resources with heart rate, blood pressure, and other physical responses to stressful events. Some evidence suggests that the amygdala in people with anxiety disorders is highly sensitive to novel or unfamiliar situations and reacts with a high stress response.

Obsessive-compulsive disorder (OCD) is the anxiety disorder most strongly associated with specific brain dysfunction. For example, abnormalities in a specific pathway of nerves have been linked to OCD, attention deficit disorder, and Tourette syndrome. The symptoms of the three disorders are similar and they often coexist.

A number of imaging studies have reported less volume in the hippocampus in people with post-traumatic stress disorder. This important region is related to emotion and memory storage.

Genetic Factors

Up to 50% of people with panic disorder and 40% of patients with generalized anxiety (GAD) have close relatives with the disorder. (About half of GAD patients also have family members with panic disorder, and about 30% have relatives with simple phobias.)

Obsessive-compulsive disorder (OCD) is also strongly related to a family history of the disorder. Close relatives of people with OCD are up to 9 times more likely to develop OCD themselves. Researchers are making progress in identifying specific genetic factors that might contribute to an inherited risk. Of particular interest are genes that regulate specific neurotransmitters (brain chemical messengers), including serotonin and glutamate. Recent research has suggested that the SLC1A1 gene, which is associated with glutamate regulation, may play an important role in early-onset OCD in boys. Research is also beginning to pinpoint regions on specific chromosomes (1, 3, 7, 6, 9, 15) that may contain genes linked to OCD.

However, there are no genetic tests to date that can identify patients at risk for anxiety disorders.

Resources

www.nimh.nih.gov -- National Institute of Mental Health
www.adaa.org -- Anxiety Disorders Association of America
www.nami.org -- National Alliance on Mental Illness
www.psych.org -- The American Psychiatric Association
www.apa.org -- The American Psychological Association
www.istss.org -- International Society for Traumatic Stress Studies
www.ncvc.org -- National Center for Victims of Crime
www.ncptsd.va.gov -- National Center for Post-Traumatic Stress Disorders
www.rainn.org -- Rape, Abuse, and Incest National Network
www.aacap.org -- American Academy of Child and Adolescent Psychiatry
www.aabt.org -- Association for Behavioral and Cognitive Therapies
www.ocfoundation.org -- Obsessive Compulsive Foundation

References

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Reviewed last on: 1/22/2009
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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