By Akshitha Mamidi, BS

Introduction

Postpartum depression (PPD) is a complex and multifactorial condition that transcends simple “baby blues” with far-reaching implications for both the mother and child. It has been established that PPD is not caused solely by genetic factors but rather a combination of genetics and socioeconomic factors, such as financial strain, low socioeconomic status, or lack of a strong social support system. Affecting one in ten new mothers, it goes undiagnosed by health professionals in 50% of those suffering from PPD. 

Given the circumstances, understanding the biological mechanisms behind PPD can be empowering for those struggling. Feelings of guilt and shame can subside when women can take full agency over their treatment options and know that PPD is real, and rooted in biological changes. 

There are three main biological aspects that I will cover in this post, briefing readers on how they work with each other and affect the body as a whole. 

1. Hormonal Shifts: 

It has been demonstrated time and time again that psychiatric symptoms are exacerbated during the menstruation cycle primarily due to the estrogen-progesterone relationship. With this in mind, people during pregnancy and after pregnancy should practice giving themselves some grace as their bodies are experiencing hormone levels fluctuating for nine months straight. 

• Estrogen and Progesterone: During pregnancy, levels of estrogen and progesterone are gradually increasing until delivery. Progesterone serves many roles during pregnancy, one of them being suppressing the mother’s immunologic response to fetal antigens. Estrogen allows for the formation of the placenta and further vascularization. Both hormones are crucial in ensuring a healthy pregnancy. These hormones serve cognitive functions as well, working in memory, and estrogen has even been established to affect endorphin (“feel-good” chemical) levels as well. However, shortly after delivery, these hormone levels drop dramatically, which can contribute to mood swings, irritability, and feelings of sadness. The postpartum drop in estrogen is particularly significant. Estrogen has mood-regulating effects, and its abrupt decrease can lead to feelings of depression and anxiety. In some women, this hormonal crash is too abrupt, contributing to PPD.
• Oxytocin: Responsible for maternal tasks such as lactation, labor and infant bonding, this hormone is theorized to play a role in PPD. Its mood-stabilizing effects have been studied in terms of major depressive disorder (MDD), but more research is yet to be done in connection with its role in PPD. Low oxytocin levels post-birth might contribute to emotional instability and depressive symptoms in some women. Research has shown that mothers with higher levels of oxytocin report happier moods and better caregiving actions. Preliminary studies suggest taking oxytocin intranasal to relieve some PPD symptoms. 

2. Genetics: 

While hormonal fluctuations are a prominent factor in postpartum depression, genetics also play a significant role in determining who might be more susceptible to the condition. Studies suggest that women with a family history of depression or other mood disorders are at a higher risk of developing PPD. Compared to MDD, there is a greater chance of PPD being heritable among generations. However, unlike other psychiatric disorders, genetics is not sufficient to cause PPD. There is a strong influence of epigenetics, the impact of behavior and environment on gene function, in the development and triggering of PPD. An example of epigenetics in PPD is the altered DNA methylation pattern observed in the oxytocin receptor gene (OXTR). As mentioned prior, oxytocin’s role is directly linked to social bonding and mood regulation. 

3. Neurotransmitters: The Brain’s Chemical Messaging System

Neurotransmitters are chemical messengers primarily in the brain, responsible for regulating mood, behavior, and emotional responses. Despite serving as chemical messengers like hormones, they differ in that they are often transmitted directly to their target with a shorter period of action.  

• Serotonin: This neurotransmitter acts on the body to regulate happiness, sexual behavior, and hunger amongst other things. The drop in estrogen-progesterone levels after birth is linked to serotonin levels and causes them to rapidly decrease. Furthermore, mutations in the serotonin receptor gene are linked to increased incidence of PPD. 
• Dopamine: The commonly heard “reward” neurotransmitter, dopamine affects motivation, pleasure, and mood. A decrease in dopamine levels post-birth may contribute to anhedonia (the inability to feel pleasure), one of the core symptoms of PPD. 

Together, genetic predispositions, hormonal imbalances, and neurotransmitter levels all contribute to PPD. Understanding the science behind it will allow mothers with PPD to feel empowered to advocate for themselves and their health. Treatment options, whether it be therapy, medications, or something else, can ensure that women will overcome PPD and lead fulfilling and joyful lives with their children. PPD’s underpinnings, rooted in the natural changes of the body during pregnancy, will be further studied in an effort to increase both awareness and treatment options and access.

About the Author

Akshitha Mamidi, BS

Akshitha Mamidi, BS, is a recent University of California, Davis graduate applying to medical school. Her interests lie in sexual/reproductive health and gender-affirming care. In her free time, Akshitha loves to watch basketball, read, and play with her dog.

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