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Biology 103
2002 First Paper
On Serendip

The Science of Shyness: The Biological Causes of Social Anxiety Disorder

Adrienne Wardy

Although many people are unaware of its existence, social anxiety disorder is the third most common psychiatric disorder, after depression and alcoholism, according to the Medical Research Council on Anxiety Disorders (1). To paraphrase the Diagnostic and Statistical Manual of the American Psychiatric Association's definition of social anxiety disorder or social phobia it is: "A persistent fear of one or more social or performance situations in which the person is exposed to unfamiliar people or to possible scrutiny by others...The avoidance, anxious anticipation, or distress in the feared social or performance situation(s) interferes significantly with the person's normal routine" (2). Although those who suffer from social anxiety disorder (SAD) are often perceived as shy, their condition is much more extreme than shyness. Unlike shyness, it is not simply a personality trait; it is a persistent fear that must have deeper roots than environmental causes.

As an anxiety disorder, SAD is classified amongst panic disorder, obsessive- compulsive disorder, posttraumatic stress disorder, and generalized anxiety disorder

(3). The question is: what causes this behavior to occur? Is it simply a result of environment or are there biological reasons? Although the present knowledge on SAD is incomplete, there are several causes that are suspected: "a combination of genetic makeup, early growth and development, and later life experience"

(4). It is my hypothesis that, in addition to environmental causes, there are also biological causes of SAD. According to current research, there is compelling evidence that brain chemicals and genetics contribute to the development of SAD.

Jerome Kagan, Ph.D. has researched the genetic causes of SAD at Harvard. In his study of children from infancy to adolescence he discovered that "10-15% of children to be irritable infants who become shy, fearful and behaviorally inhibited as toddlers, and then remain cautious, quiet, and introverted in their early grade school years. In adolescence, they had a much higher than expected rate of social anxiety disorder." This evidence suggests, of course, that people are born with SAD, which indicates that there are biological factors that contribute to its development, not simply environmental factors. Kagan also discovered a common physiological trait in these particular children: they all had a high resting heart rate, which rose even higher when the child was faced with stress. Again, this physiological trait suggests the biological causes of SAD. In this study, Kagan also found evidence that linked the causes of SAD with genetics: the parents of the children with SAD have increased rates of social anxiety disorder as well as other anxiety disorders. There is also other research that suggests that SAD has genetic causes. According to The American Psychiatric Association: "anxiety disorders run in families. For example, if one identical twin has an anxiety disorder, the second twin is likely to have an anxiety disorder as well, which suggests that genetics-possibly in combination with life experiences-makes some people more susceptible to these illnesses" (3).

Evidence of anxiety is also apparent in the animal kingdom, which suggests that it is not simply the result of nurturing, it is an inherent attribute. In the book Fears, Phobias, and Rituals, Isaac Marks found that birds avoided prey that had markings similar to the "vertebrate eye," eye-like markings on other animals, such as moths. In his experiment, these eye-spots were rubbed off of moths. As a result, they were less likely to be eaten and more likely to escape from a predator. Marks concluded that the birds feel scrutinized by the gaze of another animal and thus avoid the "eyes," much like humans with social anxiety avoid situations in which they feel scrutinized or avoid eye-contact. His research suggests that biological factors influence a form of social anxiety in animals.

In addition to genetic causes, there is also evidence that SAD is caused by chemical disturbances in the brain. It is probable that four areas of the brain are involved in our anxiety-response system: the brain stem, which controls cardiovascular and respiratory functions; the limbic system, which controls mood and anxiety; the prefrontal cortex, which makes appraisals of risk and danger; and the motor cortex, which controls the muscles. These parts are supplied with three major neurotransmitters: norepinephrine, serotonin, and gamma aminobutyric acid, all of which play a role in the regulation of arousal and anxiety. Research shows that "dysregulation of neurotransmitter function in the brain is thought to play a key role in social phobia. Specifically dopamine, serotonin, and GABA dysfuncition are hypothesized in most cases of moderate to severe SP." Researchers continue to investigate whether neurocircuits play a role in the disorder. If this hypothesis proves to be true, it will clarify that there are genetic causes to SAD (1). However, the neurobiological information alone clarifies that there are biological causes to SAD.

Although research continues to be conducted on the causes of social anxiety disorder, it is apparent that there are genetic and neurobiological causes. Of course, psychological modeling, or environmental circumstances may also be a factor in the development of SAD; however, there is compelling evidence that chemicals in the brain also cause the anxiety. Research has also concluded that those who suffer from SAD are likely to have a family member with SAD or another anxiety disorder, which supports the hypothesis that there are genetic causes to SAD, as well.


1)"; Provides information on the neurobiological causes of social anxiety.
2); Provides the DSM-IV of the American Psychiatric's Association's definition of social anxiety disorder
3); Public information from the American Psychiatric Association.
4); A website that provides information on research conducted on the causes of social anxiety.

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