The bias in threat-related amygdala reactivity associated with the 5-HTTLPR S allele is positioned to drive the polymorphism’s associations with altered mood and affective disorders, especially in interaction with exposure to environmental stressors and trauma. Evidence from animal and human studies demonstrates that the amygdala mediates both physiological (e.g., autonomic reactivity) and behavioral (e.g., reallocation of attentional resources) effects that allow an individual to respond to environmental and social challenges (54). Neuroimaging studies have reported positive correlations between indices of anxiety and amygdala reactivity to affective stimuli (especially threatening stimuli) (55). Such findings demonstrate that variability in the magnitude of threat-related amygdala reactivity predicts individual differences in sensitivity to environmental threat and stress.
