Background: We investigated the differential effects of serotonergic and noradrenergic antidepressants on brain activation in patients with major depressive disorder during a Stroop task. We predicted that pretreatment hyperactivity in the rostral anterior cingulate cortex would predict better treatment outcomes.
Methods: In total, 20 patients underwent naturalistic open-label clinical treatment with citalopram (n = 12) or reboxetine (n = 8). We performed functional magnetic resonance imaging at baseline and after 6 weeks of treatment.
Results: There were no significant group differences in clinical characteristics, treatment outcomes or baseline fMRI activations. The group by time interaction revealed significant voxels in the right amygdala-hippocampus complex (p < 0.05, family-wise error corrected by use of the bilateral amygdala and hippocampus mask image as a small volume), indicating a posttreatment blood oxygen level- dependent signal decrease in the citalopram group. Pretreatment hyperactivity in the rostral anterior cingulate cortex was not related to symptom improvement.
Limitations: Our study was a nonrandomized clinical trial.
Conclusion: These results indicate that serotonergic and noradrenergic antidepressants have a differential effect on brain activity, especially in the amygdala and hippocampus.