Some scientists hypothesize that social phobia is related to an imbalance of the brain chemical serotonin. Sociability is also closely tied to dopamine neurotransmission. Low D2 receptor binding is found in people with social anxiety. The efficacy of medications which affect Serotonin and Dopamine levels also indicates the role of these pathways. There is also increasing focus on other candidate transmitters, e.g. Noradrenalin, which may be over-active in social anxiety disorder, and the inhibitory transmitter GABA.
Individuals with social anxiety disorder have been found to have a hypersensitive amygdala, for example in relation to social threat cues (e.g. someone might be evaluating you negatively), angry or hostile faces, and while just waiting to give a speech. Recent research has also indicated that another area of the brain, the 'Anterior Cingulate Cortex', which was already known to be involved in the experience of physical pain, also appears to be involved in the experience of 'social pain', for example perceiving group exclusion