The Shyness & Social Anxiety Workbook
32make up human DNA. This work has made it possible for scientists to study 
particular genes that may be involved in the development of social anxiety 
disorder and many other conditions, using research methods known as 
linkage studies  and association studies .
So, what do we know about the role of genetics in social anxiety disorder? Most of 
the studies to date on genetics and social anxiety disorder have been twin studies (for 
instance, Kendler, Karkowski, and Prescott 1999; Kendler et al. 2001; Stein, Jang, and 
Livesley 2002), and there has also been a small number of molecular genetics studies (for 
example, Lochner et al. 2007). Generally, twin studies have found modest to moderate 
levels of heritability for social anxiety disorder, suggesting that although genetics plays a 
role, other factors such as a person’s environment and experiences are also very impor -
tant. Molecular genetics studies are just beginning in the area of social anxiety, and over 
time they should help to uncover which genes are most important in the development 
of this problem.
Two personality traits closely related to social anxiety appear to be heritable as well, 
with heritability estimates  (the extent to which the transmission of a trait across generations is 
due to genetics) being close to 50 percent across a wide range of studies (Plomin 1989). 
One of these traits, called neuroticism , is a general tendency to feel distressed, anxious, 
nervous, and worried. The other trait, called introversion , is a tendency to be inwardly 
focused and socially withdrawn. Not surprisingly, shyness and social anxiety tend to be