Having a baby should be one of the happiest and most important events in a woman’s life. However, it can also be a difficult and quite stressful task. Many physical and emotional changes can occur to a woman during the time of her pregnancy as well as following the birth of her child. These particular changes can leave a new mother feeling sad, anxious, afraid and confused. For many women, these feelings, which are known as baby blues, go away fairly quickly. But when they do not go away or rather they get worse, a woman may be experiencing the effects of postpartum depression (PPD). Abrupt hormone withdrawal is the most obvious change in immediate postpartum, but clues to the mood disturbance may lie in the deregulation of neuroendocrine systems, including how hormones affect neurotransmitters and their actions within the brain.
The baby blues are common for numerous reasons. The baby’s crying and the mother’s interrupted sleep and breast-feeding are enough to make any woman feel irritable if not overwhelmed. The onset of postpartum depression, on the other hand, is believed to be caused by chemical imbalances in the brain; specifically shifts in hormone levels. According to postpartum Support International (PSI), the theory to date suggests that a sharp drop in estrogen and progesterone following delivery is the culprit.1
Ovarian steroids play an important regulatory role in a women’s general sense of wellbeing. Studies have found significant positive correlations between the onset of PPD and postpartum withdrawal of estrogen and progesterone levels.2
Aside from estrogen’s many roles in our developmental health, it is also known to be a neuro-stimulant with anti-depressive effects. High levels of estrogen produce an imbalance in the system that aggravates symptoms of anxiety. On the other hand, low levels of estrogen can lead to episodes of depression.3
A deficiency of progesterone is also a factor in postpartum depression. When estrogen levels are high and progesterone levels low, patients would exhibit extreme rage followed by self-defeating behavior. This is not surprising because the largest concentration of progesterone receptors is in the limbic area of the brain, which is the center of emotion; also called the “area of rage and violence”.3
Both estrogen and progesterone hormones have been found to alter dopamine activity. "Without estrogen, more than 30 percent of all the dopamine neurons disappeared in a major area of the brain that produces the neurotransmitter, dopamine, " said D. Eugene Redmond, Jr., professor of psychiatry and neurosurgery at Yale School of Medicine and director of the Neural Transplantation and Regeneration Program. Dopamine plays an important role in regulating our drive to seek out rewards, as well as our ability to obtain a sense of pleasure. Low dopamine levels may in part explain why depressed people don’t derive the same sense of pleasure out of activities.4
Another hormone that could trigger postpartum depression is the corticotropin-releasing hormone (CRH). Several lines of evidence suggest the possibility that increased CRH may be a risk factor for PPD. When we are under stress, the hypothalamus secretes CRH, which increases the amount of Cortisol in the blood. Cortisol raises blood sugar levels and maintains normal blood pressure, which helps us perform well under stress. During the last trimester of pregnancy, the placenta secretes so much CRH into the blood that the levels increase threefold. When CRH levels are high, the hypothalamus releases less CRH. The sudden disappearance of the placenta after delivery results in a sharp drop of CRH levels. It takes a while for the hypothalamus to get the signal that it needs to start making more CRH again. It has been suggested that this may explain the occurrence of postpartum depressive disorders.5
Postnatal depression is also believed to be caused by a deficiency of neurotransmitters specifically serotonin and norepinephrine. These neurotransmitters are fundamental to health because they transmit nerve impulses throughout the nervous system, and have a profound effect on mood and self-esteem.
Serotonin is a neurotransmitter produced in the brain and is often referred to as the ‘feel good’ hormone. What happens during pregnancy is that the exchange between the blood of mother and fetus is courtesy of the placenta regulating levels of serotonin. After birth, when the fetus and placenta are gone, blood continues flowing from the mother’s uterine until platelets move in to stop it. Serotonin levels begin to rise and interact with receptors on the smooth muscle of the uterus. This stimulates the production of interleukin-1 beta (a protein), which creates more serotonin transporters on the neurons when they are not needed. Until interleukin-1 beta levels normalize, there is too little communication between serotonergic neurons leading to postpartum depression.6
In addition, the brain synthesizes serotonin and dopamine in line with levels of norepinephrine. Our adrenal glands are responsible for producing the stress hormones of norepinephrine. During pregnancy, the changes in the balance of hormones can cause exhaustion to the adrenal gland, which in turn affects norepinephrine and serotonin productions simultaneously.
Another line of research has investigated linkage between stress, depression, and norepinephrine. Norepinephrine helps our body to recognize and respond to stressful situations. Researchers suggest that people who are vulnerable to depression may have a system that doesn’t handle the effects of stress very effectively.7
Postpartum depression may be affected by many factors, including our social and physical environment, diet, and daily sleep patterns, just to name a few. But the reality is that those same factors affect our hormones, which regulate our brain’s response system. Steroid hormones, especially estrogens and progesterone, are the most powerful chemical signals affecting the brain. Changes in the levels of these ovarian hormones influence neurotransmitters such as dopamine and serotonin, which affect moods.