Immune System Alterations and Postpartum Mental Illness: Evidence From Basic and Clinical Research

Increased postpartum anxiety symptoms after perinatal SARS-CoV-2 infection in a large, prospective pregnancy cohort in New York City

Numerous studies reported an increase of postpartum mood symptoms during the COVID-19 pandemic. Yet, the link between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and perinatal mental health is less well understood. We investigated the associations between prenatal SARS-CoV-2 infection and postpartum depressive and anxiety symptoms, including examinations of infection timing and pandemic timeline. We included 595 participants from Generation C, a prospective pregnancy cohort in New York City (2020-2022). Prenatal SARS-CoV-2 infection was determined via laboratory or medical diagnosis. Depression and anxiety symptoms were measured 4-12 weeks postpartum using the Edinburgh Postnatal Depression Scale (EPDS) and Generalized Anxiety Disorder questionnaire (GAD), respectively. Quantile regressions were conducted with prenatal SARS-CoV-2 infection as exposure and continuously measured EPDS and GAD scores as outcomes. We reran the analyses in those with COVID-19-like symptoms in the trimester during which infection occurred. 120 (20.1%) participants had prenatal SARS-CoV-2 infection. After adjusting for socio-demographic, obstetric and other maternal health factors, prenatal SARS-CoV-2 infection was associated with higher median postpartum anxiety scores (b = 0.55, 95% CI = 0.15; 0.96). Late gestation infection (b = 1.15, 95% CI = 0.22; 2.09) and symptomatic infection (b = 1.15, 95% CI = 0.12; 2.18) were also associated with higher median postpartum anxiety scores. No associations were found with depressive symptoms. The associations were not moderated by time since the start of the pandemic. This study suggests that prenatal SARS-CoV-2 infection increases the risk of postpartum anxiety symptoms among participants reporting median anxiety symptoms. Given that this association was not affected by pandemic timing and that SARS-CoV-2 transmission continues, individuals infected with SARS-CoV-2 during pregnancy should be monitored for postpartum anxiety symptoms.

Mitochondrial might: powering the peripartum for risk and resilience

The peripartum period, characterized by dynamic hormonal shifts and physiological adaptations, has been recognized as a potentially vulnerable period for the development of mood disorders such as postpartum depression (PPD). Stress is a well-established risk factor for developing PPD and is known to modulate mitochondrial function. While primarily known for their role in energy production, mitochondria also influence processes such as stress regulation, steroid hormone synthesis, glucocorticoid response, GABA metabolism, and immune modulation - all of which are crucial for healthy pregnancy and relevant to PPD pathology. While mitochondrial function has been implicated in other psychiatric illnesses, its role in peripartum stress and mental health remains largely unexplored, especially in relation to the brain. In this review, we first provide an overview of mitochondrial involvement in processes implicated in peripartum mood disorders, underscoring their potential role in mediating pathology. We then discuss clinical and preclinical studies of mitochondria in the context of peripartum stress and mental health, emphasizing the need for better understanding of this relationship. Finally, we propose mitochondria as biological mediators of resilience to peripartum mood disorders.

Microglia depletion facilitates the display of maternal behavior and alters activation of the maternal brain network in nulliparous female rats

The peripartum period is accompanied by peripheral immune alterations to promote a successful pregnancy. We and others have also demonstrated significant neuroimmune changes that emerge during late pregnancy and persist postpartum, most prominently decreased microglia numbers within limbic brain regions. Here we hypothesized that microglial downregulation is important for the onset and display of maternal behavior. To test this, we recapitulated the peripartum neuroimmune profile by depleting microglia in non-mother (i.e., nulliparous) female rats who are typically not maternal but can be induced to behave maternally towards foster pups after repeated exposure, a process called maternal sensitization. BLZ945, a selective colony-stimulating factor 1 receptor (CSF1R) inhibitor, was administered systemically to nulliparous rats, which led to ~75% decrease in microglia number. BLZ- and vehicle-treated females then underwent maternal sensitization and tissue was stained for ∆fosB to examine activation across maternally relevant brain regions. We found BLZ-treated females with microglial depletion met criteria for displaying maternal behavior significantly sooner than vehicle-treated females and displayed increased pup-directed behaviors. Microglia depletion also reduced threat appraisal behavior in an open field test. Notably, nulliparous females with microglial depletion had decreased numbers of ∆fosB+ cells in the medial amygdala and periaqueductal gray, and increased numbers in the prefrontal cortex and somatosensory cortex, compared to vehicle. Our results demonstrate that microglia regulate maternal behavior in adult females, possibly by shifting patterns of activity in the maternal brain network.

Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats

Postpartum depression (PPD) is a major psychiatric complication of childbirth, affecting up to 20% of mothers, yet remains understudied. Mitochondria, dynamic organelles crucial for cell homeostasis and energy production, share links with many of the proposed mechanisms underlying PPD pathology. Brain mitochondrial function is affected by stress, a major risk factor for development of PPD, and is linked to anxiety-like and social behaviors. Considering the importance of mitochondria in regulating brain function and behavior, we hypothesized that mitochondrial dysfunction is associated with behavioral alterations in a chronic stress-induced rat model of PPD. Using a validated and translationally relevant chronic mild unpredictable stress paradigm during late gestation, we induced PPD-relevant behaviors in adult postpartum Wistar rats. In the mid-postpartum, we measured mitochondrial function in the prefrontal cortex (PFC) and nucleus accumbens (NAc) using high-resolution respirometry. We then measured protein expression of mitochondrial complex proteins and 4-hydroxynonenal (a marker of oxidative stress), and Th1/Th2 cytokine levels in PFC and plasma. We report novel findings that gestational stress decreased mitochondrial function in the PFC, but not the NAc of postpartum dams. However, in groups controlling for the effects of either stress or parity alone, no differences in mitochondrial respiration measured in either brain regions were observed compared to nulliparous controls. This decrease in PFC mitochondrial function in stressed dams was accompanied by negative behavioral consequences in the postpartum, complex-I specific deficits in protein expression, and increased Tumor Necrosis Factor alpha cytokine levels in plasma and PFC. Overall, we report an association between PFC mitochondrial respiration, PPD-relevant behaviors, and inflammation following gestational stress, highlighting a potential role for mitochondrial function in postpartum health.

Risk of postpartum readmission for depression in relation to ischaemic placental disease: a population-based study

Background

There are limited data on postpartum readmissions for depression in the United States (US). Specifically, the extent to which ischaemic placental disease (IPD) during pregnancy predisposes patients to develop postpartum depression remains poorly understood. We investigated whether IPD is associated with postpartum readmission for new-onset depression in the first year after delivery.

Methods

In this population-based study, the 2010-2018 Nationwide Readmissions Database was utilised to evaluate rates of postpartum readmission for depression within the calendar year of delivery hospitalisation among patients with and without IPD. IPD was defined as preeclampsia, placental abruption, or small for gestational age (SGA) birth. We expressed associations between IPD and depression readmission based on a confounder-adjusted hazards ratio (HR) with a 95% confidence interval (CI).

Findings

Of 33.3 million delivery hospitalisations, 3,027,084 (9.1%) had IPD. The total follow-up among those with and without IPD were 17,855,830 and 180,100,532 person-months, respectively, with a median follow-up of 5.8 months for both groups. Rates of depression readmission were 95.7 (n = 17,095) and 37.5 (n = 67,536) per 100,000 readmissions among patients with and without an IPD, respectively (HR, 2.39; 95% CI, 2.32-2.47); this risk was the highest for preeclampsia with severe features (HR, 3.14; 95% CI, 3.00-3.29). Patients had a greater risk of readmission if they had any two forms of IPD (HR, 3.02; 95% CI, 2.75-3.33), and those with a concurrent diagnosis of preeclampsia and abruption posed the highest risk (HR, 3.23; 95% CI, 2.71-3.86).

Interpretation

These findings suggested that patients with IPD are at a substantially increased risk of readmission for depression within a year following delivery. This study underscores the need for increased surveillance, improved detection, and faster treatment of depression in this vulnerable population.

Funding

This was an unfunded project.

Sex differences in depression: An immunological perspective

Depression is a heterogenous disorder with symptoms that present differently across individuals. In a subset of people depression is associated with alterations of the immune system that may contribute to disorder onset and symptomology. Women are twice as likely to develop depression and on average have a more sensitive adaptive and innate immune system when compared to men. Sex differences in pattern recognition receptors (PRRs), release of damage-associated molecular patterns (DAMPs), cell populations, and circulating cytokines play a critical role in inflammation onset. Sex differences in innate and adaptive immunity change the response of and repair to damage caused by dangerous pathogens or molecules in the body. This article reviews the evidence for sex specific immune responses that contribute to the sex differences in symptoms of depression that may account for the higher rate of depression in women.

Assessment of the Postpartum Emotional Wellbeing among Women Participating and Not Participating in Antenatal Classes

The perinatal period is associated with an increased risk of emotional disorders. Exposure to stress impacts the functioning of the maternal brain, also shaping the developmental processes of the child's brain. To assess the emotional wellbeing of women participating and not participating in antenatal classes. The study involved a group of 200 women divided into two groups: the study group, participants of the antenatal classes (N = 100), and the control group, not participating in the antenatal classes (N = 100). The Edinburgh Postnatal Depression Scale (EPDS) and Mini-COPE inventory were used. EPDS was administered at two time points: on the 2nd day of puerperium and 6 weeks after the delivery, while Mini-COPE inventory was applied once during pregnancy. Severe symptoms of depression on the 2nd day after childbirth concerned 16.0% of the women (N = 15) participating in the antenatal classes and 11.0% of the controls (N = 11). Intensification of depressive symptoms 6 weeks after the delivery occurred in 19.5% of the females attending antenatal classes (N = 17) and 18.8% of the controls (N = 18). Severe symptoms of depression 6 weeks after the delivery in the group of women participating in antenatal classes were significantly related to adopting helplessness to cope with stress and a sense of being accepted by the husband/partner, family, and society. In the case of women not participating in antenatal classes, the severity of symptoms of depression 6 weeks after the delivery was slightly related to the sense of acceptance by the husband/partner, family, and society. Apart from identifying risk factors for emotional disorders in pregnancy, it is worth taking into account whether a woman participated in antenatal classes when planning the care in the perinatal period. This factor can be a potential protective factor in preventing emotional problems after childbirth.