Why Do You Have These Fears?
33Effects of the Brain and Neurotransmitters
Compared with other psychological problems, including other anxiety disorders, 
studies examining the biological factors underlying social anxiety often have failed to 
obtain signiﬁcant ﬁndings. For example, research examining hormonal factors, sleep pat -
terns, and heart functioning has often failed to ﬁnd differences between people with 
social anxiety disorder and people without signiﬁcant social anxiety. 
However, a number of studies have found increased levels of activity in particular 
parts of the brain during periods of social anxiety. For example, scientists have found 
that people with social anxiety disorder experience increased activity in a part of the 
brain called the amygdala  when looking at pictures of harsh faces (Phan et al. 2006; Stein 
et al. 2002; Straube et al. 2004). The amygdala is part of the limbic system  and is activated 
when we experience the emotion of fear. During public speaking, there also appears 
to be more activation in the amygdala among people with social anxiety disorder than 
among people without this problem (Phan et al. 2006).
As reviewed by Britton and Rauch (in press), other areas of the brain that have been 
found to be activated during social anxiety include the anterior  cingulate cortex  (an area that 
is involved in controlling emotions, thought, and heart rate, among other functions), the 
medial prefrontal cortex  (a section of the brain that is involved in complex cognition, per -
sonality expression, and social behavior), the insular cortex  (a section of the limbic system 
that is involved in the experience of basic emotions, including fear), and the hippocampus