What Are the Genetic Causes of Social Anxiety Disorder?

Genes may play a role in social anxiety disorder.
Genes may play a role in social anxiety disorder. Mario Tama / Getty Images

Is anxiety genetic? If you have been diagnosed with social anxiety disorder (SAD), you may wonder what caused you to develop the illness.

Genes and Social Anxiety Disorder

If you have a first degree relative with SAD, you may be 2 to 3 times more likely to develop the disorder. The genetic component of social anxiety disorder, also known as the “heritability” of the disorder, has been estimated at around 30% to 40%, meaning that roughly one third of the underlying causes of SAD come from your genetics.

Heritability is the proportion of variation in a phenotype (trait, characteristic or physical feature) that is thought to be caused by genetic variation among individuals. The remaining variation is usually attributed to environmental factors. Studies of heritability typically estimate the proportional contribution of genetic and environmental factors to a particular trait or feature.

So far, researchers have not found a particular genetic makeup linked to SAD. They have, however, found specific chromosomes linked to other anxiety disorders such as agoraphobia and panic disorder.

Because SAD shares many characteristics with other anxiety disorders, it is likely that a specific chromosome structure will eventually be connected to the disorder. If you are diagnosed with SAD, you probably have specific genes that made you more prone to developing the disorder.

Neurotransmitters and Social Anxiety Disorder

If you have social anxiety disorder, there are likely imbalances of certain chemicals in your brain, known as neurotransmitters. These neurotransmitters are used by your brain to send signals from one cell to another.

Four neurotransmitters may play a role in SAD: norepinephrine, serotonin, dopamine and gamma-aminobutyric acid (GABA).

People with social anxiety disorder have been shown to have some of the same imbalances of these neurotransmitters as people with agoraphobia and panic disorder. Researchers are just starting to understand exactly how these chemicals are related to SAD.

Understanding how these brain chemicals relate to social anxiety disorder is important to determine the best medications for treatment.

Brain Structures and Social Anxiety Disorder

Just as x-rays are used to “see inside” your body, the same can be done for your brain. Medical researchers use a technique called “neuroimaging” to create a picture of the brain.

For mental disorders, researchers are usually looking for differences in blood flow in specific areas of the brain for people who are known to have a particular disorder.

We know that four areas of the brain are involved when you experience anxiety:

  • the brain stem (controls your heart rate and breathing)
  • the limbic system (effects your mood and anxiety level)
  • the prefrontal cortex (helps you to appraise risk and danger)
  • the motor cortex (controls your muscles)

One study of blood flow in the brain found differences in the brains of social phobics when speaking in public. For this study, they used a type of neuroimaging called “Positron Emission Tomography” (PET).

The PET images showed that people with social anxiety disorder had increased blood flow in their amygdala, a part of the limbic system associated with fear.

In contrast, the PET images of people without SAD showed increased blood flow to the cerebral cortex, an area associated with thinking and evaluation. It seems that or people with social anxiety disorder, the brain reacts to social situations differently than people without the disorder.

Behavioral Inhibition in Childhood 

Do you know a toddler or young child who always becomes extremely upset when confronted with a new situation or unfamiliar person? When faced with these types of situations does the child cry, withdraw or seek the comfort of a parent?

This type of behavior in toddlers and young children is known as behavioral disinhibition. Children who show behavioral disinhibition as a toddler are at greater risk for developing SAD later in life.

Because this temperament shows up at such a young age, it is likely an inborn characteristic and the result of biological factors.

If you are concerned that your child is excessively withdrawn or fearful in new situations it may be helpful to discuss your worries with a professional. Since we know that behaviorally disinhibited toddlers are more likely to become socially anxious children and socially phobic adults, any kind of early intervention may help prevent more serious problems later in life.

Closing Thoughts

There is no single cause of SAD. In most people, the disorder is the result of a combination of environmental and biological factors. Environmental factors relate to your upbringing and experiences, and biological factors are things like your genetic makeup, brain chemistry and inborn personality style. In short, researchers are still seeking to understand the genetic underpinnings of social anxiety disorder. 

Sources:

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Washington, DC: Author; 2013.

Hales RE, Yudofsky SC. (Eds.). The American Psychiatry Publishing Textbook of Clinical Psychiatry. Washington, DC: American Psychiatric; 2003.

Tillfors M, Furmark T, Marteinsdottir I, et al. Cerebral Blood Flow in Subjects with Social Phobia During Stressful Speaking Tasks: A PET Study. Am J Psychiatry. 2001;158(8):1220-1226. doi:10.1176/appi.ajp.158.8.1220.

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