Abstract
The short allele of the serotonin-transporter-linked promoter region (5-HTTLPR) polymorphism is associated with increased amygdala activation in response to emotional stimuli. Although top-down processes may moderate this association, available evidence is conflicting, showing the genotype influence on amygdala reactivity to be either decreased or increased during emotion regulation. Because the effects of the 5-HTTLPR polymorphism on amygdala reactivity are also conditional on self-reported life stress, differences in life stress exposure may account for this apparent discrepancy. Here, we hypothesized that self-reported life stress would moderate the relationships between genotype, cognitive appraisal, and amygdala reactivity. Forty-five healthy never-depressed subjects were presented with emotional stimuli and performed two cognitive tasks: a self-referential task and an emotion-labeling task. Life-stress exposure was measured through a semistructured interview. First, there was a genotype × condition interaction in the right amygdala: short allele carriers displayed increased amygdala activation and decreased functional connectivity with the subgenual anterior cingulate cortex in self-referential processing versus emotion labeling. Second, in line with our hypothesis, there was a genotype × condition × stress interaction in bilateral amygdala the amygdala activation during self-referential processing was negatively correlated with self-reported life stress in short allele carriers and positively in individuals homozygous for the long allele, whereas an opposite pattern was observed during emotion labeling. These results confirm that the influence of the 5-HTTLPR polymorphism on amygdala reactivity is at least partially under cognitive control. Additionally, they suggest that measuring life stress exposure is a critical step when imaging genetics.