The maternal reward system in postpartum depression

Abstract

The experience of motherhood is most often emotionally positive and rewarding, but for many new mothers suffering from postpartum depression (PPD), this is not the case. Preclinical and clinical research has sought to uncover brain changes underlying PPD in order to gain a better understanding of how this disorder develops. This review focuses on the mesolimbic dopamine system, particularly the ventral tegmental area-nucleus accumbens pathway which has been implicated in the regulation of critical functions disrupted in PPD including mood, motivation, and mothering. Specifically, we discuss normative changes in the mesolimbic system during motherhood in both rodents and humans and how these are impacted in PPD. We also consider modulation of mesolimbic dopamine by the hypothalamic neuropeptide oxytocin and how oxytocin-dopamine interactions regulate mood and mothering during the postpartum period. In addition to providing an overview of reward mechanisms in PPD, our goal is to highlight open questions which warrant further research.

Keywords: Depression; Dopamine; Maternal; Mesolimbic; Nucleus accumbens; Oxytocin; Postpartum; Pregnancy; Striatum.

Figure 1.

Representation of the number of studies published on postpartum depression (PPD) from 1960–2017. Numbers were generated using “postpartum depression” as a search term in PubMed. The red bar indicates when PPD was added to the DSM in 1994 as a form of major depression (MD). The gray bar represents when functional magnetic resonance imaging (fMRI) was first utilized to study the mesolimbic reward system in PPD (Silverman et al. 2007). In 2013 (green bar), a peripartum onset specifier was added to the DSM-V. As of 2017 (blue bar), there have only been approximately 20 fMRI studies completed on mothers suffering from PPD. Of these, nine showed reward system changes with PPD. Adapted from Li and Chou, 2016.

Figure 2.

Simplified schematic diagram of dopamine (DA) and oxytocin (OT) neurocircuitry and findings from animal models of PPD investigating this circuit. Abbreviations: HPC, hippocampus; NAc, nucleus accumbens; PFC, Prefrontal cortex; VTA, ventral tegmental area.