Amygdala responses to unattended fearful faces: Interaction between sex and trait anxiety.

Trait anxiety and sex have been shown to separately account for some of the observed individual differences in amygdala responses to emotional stimuli, but the combined effect of both factors remains unknown. In this fMRI study, participants varying in trait anxiety scores viewed a series of superimposed face/scene composite images (containing fearful or neutral faces) and were instructed to direct attention to either the face or the scene content. We observed an interaction between sex and trait anxiety in amygdala responses to fearful faces as a function of attention. In females, higher trait anxiety was associated with a stronger amygdala response to unattended fearful faces, whereas no such relationship was present in males. This observed interaction between sex and individual differences in trait anxiety at the level of the brain may have clinical implications for a better understanding of the higher incidence of anxiety disorders in women than men.