There is no clear mandate on the exact cause of social anxiety disorder. There are many assumptions about it, which include a combination of a persons genetic make up, early childhood and adolescent experiences. It could be caused by a persons genetic predisposition. And just as physical features like eye and hair color are inherited, social anxiety disorder can also be passed on from one generation to the other. It has been proven that in some cases anxiety disorders run through generations. It has also been noticed among identical twins that if one of them has an anxiety disorder, the other is also likely to have the disorder, so there is an obvious link between anxiety disorders and ones genes.

The second commonly believed cause originated from a study of animal behavior, which says that all animals are fearful of others, especially strangers looking or staring at them. Staring is generally considered threatening behavior, and can unsettle the other person. Therefore, avoiding eye contact or averting the gaze is very common in people with social anxiety disorder. It is usually seen that fear of strangers develops in very young babies, as early as 7 months of age. Though it is natural for young children to be anxious around strangers, trauma or stress in the early years is perceived as a probable cause for this order.

It is also believed that anxiety is caused by the structure of our brain. Our brain controls all our thinking, physiological functions and behavior. Anxiety symptoms are often relieved by medicines that change the chemical balance of the brain. In fact, our anxiety response system is centered in our brain, and there are certain critical components in the brain that regulate our response to anxiety. Individuals with social anxiety disorder probably have abnormalities in the functioning of some parts of their anxiety response system.

An individuals personality may also play an important role. It has been noticed that people with low self-esteem and poor coping skills are more prone to social anxiety disorders. Whereas it may also be possible that anxiety disorder in a childs early years has led to the low self-esteem, psychologists also believe that there may be an important relationship between anxiety disorders and long-term exposure to abuse and violence.