Neurophysiology of Postpartum Depression in an Experimental Model of Pregnancy and Parturition

Overview

Understanding the neural and biological mechanisms by which reproductive hormones influence mood is critically important for public health given that postpartum depression (PPD) is the leading cause of morbidity and mortality associated with childbirth and has negative effects on infants. Using a hormone-withdrawal challenge to precipitate mood symptoms will improve our ability to identify the biological mechanisms underlying both the triggering of and susceptibility to depressive disorders in women; and will permit the prediction of those at risk for PPD and other reproductive-related mood disorders.

Affective disorders, such as PPD and other reproductive-related mood disorders, are common and constitute a significant burden for women, children, and society. However, little is known about the neurobiological mechanisms underlying depressive disorders in women. The long-term goal of this research is to 1) advance our understanding of the biological mechanisms underlying both the triggering of and susceptibility to depressive disorders in women; and 2) permit the prediction of those at risk for PPD. The objective of the current project is to examine whether those with a past episode of PPD (at "high risk" for recurrence) show differences in emotional arousal and reward processing domains relative to healthy control women (without a history of PPD) under baseline and hormone withdrawal-precipitated conditions. The central hypothesis is that reproductive hormone changes are associated with dysregulation of the neural circuits underlying emotional arousal and reward processing and consequent depressive symptoms in high-risk women. The rationale for the proposed study is that employing a scaled down model of puerperal hormonal events in high-risk women permits the identification of a group of individuals homogeneous for reproductive related affective dysfunction and, hence, the best opportunity for disentangling the specific changes in brain function due to reproductive hormones from those accompanying reproductive hormone-precipitated affective dysfunction. Moreover, identifying a neurophysiologic biomarker for hormone-related affective dysfunction provides a clear pathway for examining mechanisms of susceptibility to affective dysfunction across disorders. The investigators plan to accomplish the objectives of this application by pursuing the following specific aims: 1) to assess the effects of simulated postpartum reproductive hormone withdrawal, compared to baseline, on corticolimbic circuit activation in high-risk and control women; and 2) to examine the effects of reproductive hormone withdrawal, compared to baseline, on reward circuit activation in high-risk and control women. An additional exploratory aim is to identify a neural biomarker, characterized by corticolimbic and reward circuit dysfunction, that can be used to predict the onset of PPD. The proposed study involves experimentally manipulating reproductive hormones in euthymic women to create a scaled down version of the changes that occur at the puerperium. This endocrine manipulation paradigm will be used to examine the neurocircuitry underlying the regulation of affect and reward processing under baseline and hormone withdrawal-precipitated conditions among women who are expected to experience hormone-related affective dysregulation (n=15) and controls (n=15). In short, the investigators expect that relative to baseline, high-risk women will show greater dysregulation in neural circuits responsible for emotion processing and reward processing during hormone withdrawal than low-risk control women. The expected outcome of this research is the identification of neural circuits underlying both the susceptibility to and mediation of hormone-related affective dysfunction. Understanding these neurobiological mechanisms will subsequently improve the ability to identify those at risk for PPD, which may strengthen prevention efforts and ultimately prevent the deleterious effects of maternal depression on offspring.