Rapid Habituation of Ventral Striatal Response to Reward Receipt in Postpartum Depression

Background: Little is known about neural mechanisms of postpartum depression (PPD). Previous research notes ventral striatal activity and dopamine release increases with maternal attachment but decreases in major depressive disorder. This study tests the hypothesis that striatal response to reward is altered in PPD. Methods: Subjects underwent functional magnetic resonance imaging blood oxygenation level-dependent acquisition during a fast event-related card-guessing, monetary reward task. Time series data from an independent sample of 10 healthy mothers were used to establish the ventral striatal region of interest (ROI). Repeated-measures analysis of variance of time series data in the established ROI was then conducted for a discrete group of healthy (n = 12) and depressed, unmedicated mothers (n = 12). Results: Data from the independent sample of 10 healthy mothers established an ROI in the left ventral striatum (-13, 12, -4, 477 mm(3)), with cluster significance p < .01, corrected. There was a significant quadratic interaction of time x group [ F(1,22) = 5.22, p = .032] in this ROI in the healthy (n = 12) and depressed mothers (n = 12). This effect represents a nonlinear attenuation of ventral striatal response with time that was greater in depressed than healthy mothers. Conclusions: Rapid attenuation of ventral striatal response to reward receipt in postpartum depression might represent an important neural mechanism of postpartum depression. Additional study with infant stimuli and in relationship to mother-infant behavior is needed.