The diagnostic boundaries of social anxiety disorder (SAD) are still controversial and recent evidence suggests that the condition could be better understood as a continuum of severity, rather than a strictly circumscribed entity. Current neuroanatomical theories on SAD support the involvement of limbic structures in its pathophysiology, with an emphasis on the amygdala. Thus, the objective of this study was to investigate the hypothesis of volumetric alterations in the amygdala of subjects in different points of the social anxiety spectrum.

The sample consisted of patients with generalized SAD (n=17), subthreshold SAD (increased social anxiety without avoidance; n=13), and healthy controls (n=15). Participants underwent structural magnetic resonance scans and the volume of the bilateral amygdala was manually determined.

Significantly greater volumes of bilateral amygdala were found in socially anxious individuals. Amygdala volumes of subthreshold SAD participants fell between the values found for generalized SAD and healthy controls.

Individuals suffering from SAD have greater amygdala volumes compared to controls and this difference seems to be in agreement with the theoretical conception of SAD as a severity continuum and not as a circumscribed nosological entity.