 Social anxiety disorder SAD is an anxiety disorder characterized by excessive fear and avoidance of social situations. Selective serotonin reuptake inhibitors SSRIs are a medication commonly prescribed to treat social anxiety disorder, but as many as 50 of people with SAD do not respond to SSRIs. Current theory suggests that neurological functioning and genetics may influence a patients response to treatment. This study will examine variations in genetics and brain reactivity among people with SAD who do and do not respond to SSRIs. Through this, the study will identify neurological and genetic biomarkers that can predict responsiveness to SSRI treatment in people with SAD. 