Why Do You Have These Fears?
31So, from an evolutionary perspective, people with social anxiety disorder do not 
have an illness,  per se. Rather, they have too much of a good thing . Social anxiety is helpful in 
small doses, but when it is too intense, it can make life more difﬁcult.
Genetics and Social Anxiety
Social anxiety disorder appears to run in families. For example, a study by Stein, 
Chartier, Hazen, Kozak, et al. (1998) found that having a close relative (for example, a 
parent, sibling, or child) with generalized  social anxiety disorder (extreme anxiety in most 
social situations) made an individual ten times as likely to have social anxiety disorder, 
compared with individuals who didn’t have a socially anxious relative. In contrast, more 
narrowly focused social fears (for example, a fear of public speaking only) were less likely 
to run in families. 
Of course, the existence of social anxiety disorder in multiple family members does 
not necessarily mean that the social anxiety is transmitted by genes. Environmental 
factors (for example, learning from one’s parents and siblings) can also contribute to 
the family members sharing certain behaviors and tendencies. To tease out the effects 
of genetic inﬂuences from the effects of environment and learning, scientists have relied 
on three main types of studies:
1. Twin studies.  Twin studies examine the frequency of a problem across pairs 
of identical twins  (twins who are 100 percent genetically identical) vs. pairs of 
fraternal twins  (twins who share, on average, 50 percent of their genetic mate -
rial). Because twin pairs tend to be raised in similar environments regardless