Becoming a mother can be one of the most amazing, rewarding, and enriching experiences in life. It can also be one of the most challenging experiences you’ll ever face. My baby girl, Juliette, was born on February 15, 2015. She is now a beautiful and very energetic toddler. Juliette is most definitely the love of my life, but the past 2.5 years have come with many ups and downs.
There is this expectation that having a baby is meant to be the most joyful time in life, full of pure happiness. Within the framework of being a mother, those moments definitely exist. But in reality, they are mixed with many other difficult moments that are often accompanied by extreme lack of sleep. The truth is - being a mother comes with many unexpected challenges that no one can really prepare you for.
Because of this, motherhood can be accompanied by mental unhealth, with about 15-20% of new mothers experiencing post-partum depression. Like most forms of depression, post-partum depression is characterized by sadness, hopelessness, and anhedonia or the inability to feel pleasure. In 70% of the cases, post-partum depression is also accompanied by symptoms of anxiety.
These symptoms, of course, are occurring when there is a helpless infant that needs to be held, cradled, fed, bathed, and watched 24 hours a day. Post-partum depression then leads to some unfortunate consequences for the infant. For example, mothers with post-partum depression are often disengaged, have fewer and less affectionate interactions with the baby, and are overall less responsive and sensitive to cues from the baby. These issues lead to trouble bonding with the baby, and can cause impaired social, cognitive, and emotional development, issues that can continue into adulthood.
Proper maternal care is needed to ensure proper development of the child. Considering that 1 in 5 mothers are suffering from post-partum depression, this is a critically important issue. Surprisingly, little is known about the underlying neurobiological mechanisms of post-partum depression. Neuroscientists are starting to reveal some interesting information about the brain of mothers with post-partum depression, and they shared their most recent findings with us today at the Society for Neuroscience conference.
One research scientist, Aya Dudin, a graduate student at McMaster University, discussed her work on the involvement of the amygdala in post-partum depression. She explained that the amygdala is central to the expression of mothering as it is involved in the detection of socially and emotionally salient stimuli. For example, non-depressed mothers show a greater level of amygdala activation when looking at images of their own rather than another baby, especially when the baby has a happy expression. When imaging the brain of mothers with post-partum depression, however, you see a blunted or irregular response in the amygdala. For example, when viewing images of babies, their own or others, the response looks more like that of non-mothers. Therefore, these results suggest that normal infant-related amygdala function is needed for normal parenting.
Exposure to chronic stress during pregnancy is a major predictor of developing post-partum depression. Benedetta Leuner, Assistant Professor at the Ohio State University, took advantage of this fact to create an animal model of post-partum depression. To do this, Dr. Leuner exposed pregnant dams to a chronic stress paradigm throughout the gestational period. By doing this, she saw similar behavioral outcomes in the post-partum period to what is seen in humans with post-partum depression. First, gestational weight gain as well as pup weight at birth was reduced. Second, gestational stress caused depressive- and anxiety-like behaviors as well as anhedonia during the post-partum period. Third, motivation for and the expression of maternal behavior were impaired.
Dr. Leuner then used this animal model to assess the changes in the brain that underlie the symptoms associated with post-partum depression. She found distinct changes in the neuronal circuitry associated with both dopamine and oxytocin, two neurochemicals involved in reward and maternal behavior. Specifically, the gestational stress paradigm disrupted dopamine signaling in the nucleus accumbens by lowering dopamine content, reducing dendritic complexity (length and branching), and decreasing spine density. Reduced oxytocin signaling as indicated by reduced oxytocin fiber density and decreased oxytocin receptor density was also found in the ventral tegmental area. These results indicate that specific changes in the reward circuitry may be underlying post-partum depression.
Collectively, this research shows that mothers with post-partum depression may show altered functional and structural changes in regions involved in both emotional processing as well as reward evaluation. This is an important area of research that warrants further examination. Certainly, identification of these issues early on in the post-partum period will be instrumental in helping mothers and their babies develop healthy and loving relationships.
Julia C. Basso, PhD