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A recent study published in the Journal of Traditional Psychiatry says pregnant women with perinatal depression may be having an affect on their unborn child on a biological level, potentially putting them “at risk for developing a range of neuropsychiatric disorders.”

This is not to scare women with perinatal depression. This is to drive home the message of how important it is to find the underlying causes of perinatal depression in order to enact appropriate screening and treatment methods for the health and safety of mother and child.

Perinatal depression occurs in 10-15% of women in the U.S. according to the study which is the same level of prevalence for women in Canada.

Although we know mental health disorders can be genetic, the intent of the study was to look at the “neurobiological processes” by which prenatal depression can affect a child in the womb and beyond.

What they did was look at how the baby’s amygdala pre-frontal cortex was fairing in the third trimester of a pregnant woman with perinatal depression.

The amygdala is part of our limbic system located in the brain. The limbic system is comprised of the parts of our brain that regulate emotion, behavior and motivation. The amygdala pre-frontal cortex helps with regulating moods such as anxiety and depression. 

The study used MRIs to determine that the amygdala pre-frontal cortex in unborn infants of women with perinatal depression was demonstrating “atypical connectivity”. The infants also had an increased heart rate.

According to scientific research, altered amygdala-prefrontal connectivity has been implicated in pediatric depression.

Notes the study: “These findings suggest a potential for very early identification of risk phenotypes for the purposes of primary intervention, as well as the possibility that familial risk for psychopathology occurs, in part, through the transmission of pregnant women’s psychiatric symptoms to their children.”

Susanne Brummelte, author of Postpartum Depression: Etiology, treatment and consequences for maternal care, a review published in the Journal of Hormones and Behavior, sheds more light on the biological causes of postpartum depression (PPD). Susanne is an assistant professor in the Department of Psychology at Wayne State University in Detroit, Michigan.

Patricia: Are we close to understanding the cause/s of PPD? 

Susanne: The neurobiology or etiology of PPD can’t be well understood by the general public, as it isn’t even well understood by the scientific community yet; i.e. we really don’t know the ‘causes’ for PPD yet, (or any depressive disorder for that matter) though we have identified some contributing risk factors.

The few studies that have been conducted suggest an involvement of steroid and other hormone fluctuations (estrogens, progesterone, oxytocin as well as the stress hormone cortisol, that happen during pregnancy and the postpartum) and other neurobiological markers (such as a decrease in brain-derived neurotrophic factor (BDNF)) in women with PPD), but none of these factors alone have been ‘sufficient’ to induce or cause PPD, indicating that the etiology is highly complex.

Patricia: What we do we know about who is at risk for PPD?

Susanne: While prior depression is the greatest risk factor for PPD, approximately 40% of women will have their first episode of depression during the postpartum (Wisner et al., 2013). Thus, you do not have to have a history of depression or anxiety to develop PPD.

Patricia: Every woman experiences hormone fluctuations during pregnancy and postpartum. Why do some women develop PPD while others don’t?

Susanna: We do not fully understand why some women develop PPD and others do not. As you state correctly, every mother experiences extreme hormone fluctuations during pregnancy and parturition, but some may be more sensitive to these fluctuations than others.

This ‘estradiol-withdrawal-hypothesis’ is supported by research studies showing that women with a history of PPD are more sensitive to ovarian hormone withdrawal (Bloch et al., 2000) and that extreme fluctuations in estradiol can be correlated with increased depressive scores  (Frokiaer et al., 2015). However, we need more research to figure out the exact underlying mechanisms and neurobiology of PPD.

Though the serotonergic system received a lot of attention for being involved in major depressive disorder (MDD), there is a dearth of knowledge about the potential neurochemical changes associated with PPD. One major issue is that we often base our hypotheses about the causes of mental disorders such as MDD on the mechanism of action of the treatments.

This is how the idea of a chemical imbalance in the brain for MDD came to life, (i.e. Selective serotonin reuptake inhibitor improve the symptoms of depression, so serotonin most be involved in causing the symptoms) but there are some major flaw in these kind of assumptions (i.e. the time lag between treatment and improvement) and there is actually hardly any research to really confirm or identify a specific imbalance in MDD brains that would cause or explain MDD. And unfortunately we know even less about how hormones and neurotransmitters really regulate mood in patients with PPD.

Patricia: When will we see a biological test for PPD?

Susanne: Not any time soon. Though researchers are always looking for biomarkers to better identify and diagnose mental disorders, it is difficult to identify biomarkers if we haven’t identified the underlying etiology yet.

 

REFERENCES:

J Posner, J Cha, A K Roy, B S Peterson, R Bansal, H C Gustafsson, E Raffanello, J Gingrich, C Monk, (November 2016), Journal of Traditional Psychiatry, Alterations in amygdala–prefrontal circuits in infants exposed to prenatal maternal depression, https://www.nature.com/articles/tp2016146

SusanneBrummelteaLiisa A.M.Galeab, (2016), Journal of Hormones and Behavior, Postpartum depression: Etiology, treatment and consequences for maternal care, https://www.sciencedirect.com/science/article/pii/S0018506X15300428