We recently sat down with Dr. Sarah Blankenship to discuss her research, which focuses on the development of depression in children and particularly the transmission of depression from mothers to children. Her research has found evidence suggesting links between parenting styles, children’s physical responses and later changes in the brain, and the subsequent development of depression in children. Read this interview and learn more about her research and how it developed from studies of rodents.
During the past summer, Sarah Blankenship worked on the Birth to Five Service Delivery Models project as a Post-Doctoral Associate. She received her PhD in Neuroscience and Cognitive Science from the University of Maryland in 2017, and her research has focused on the effects of early life experiences on brain development during childhood. She is interested in looking at the underlying mechanisms that explain the link between early experience and risk for later psychopathology.
In this post, we interviewed Sarah about her research and what it means for future early childhood interventions. The full interview transcript follows:
Could you talk a little bit about your research and how it relates to child development?
At the most basic level, I’m interested in understanding why people become depressed. We know that the offspring of depressed mothers are more likely to become depressed themselves, and I’m interested in understanding how. Whenever we talk about intergenerational transmission, genetics is always a factor that is considered; however, in the case of depression, only about 37% of transmission can be explained by genetics alone. There is some evidence that the experience of interacting with a depressed parent may account for some of the other variance. This link between the parenting behaviors of depressed mothers and child development is the focus of my research.
There is an abundance of human literature linking the early parenting environment to child outcomes. However, the majority of research which has examined how parenting shapes offspring development has been done in rodents. The past twenty years of rodent research has shown us that the early parenting environment can affect offspring behavior by shaping the child’s neurobiological response to stress and, ultimately, the brain regions implicated in depressive disorders. What we see is that maladaptive parenting behaviors early in development shape the offspring’s response to stress to be longer and more intense. This means that in a stressful situation, more of the stress hormone corticosterone (cortisol in humans) is released. Too much corticosterone (or cortisol) can be neurotoxic – especially in regions that have a relatively high density of cortisol receptors. One such region that is particularly affected is the hippocampus. This is a region of the brain that plays a role in regulating the stress response (through the activation of the receptors I mentioned), controls the formation of episodic memories, and has been implicated in the etiology of depressive disorders in adults. The offspring of mothers who are less attentive to their offspring’s needs display high and increasing cortisol responses to stress, causing structural and functional changes in the hippocampus which, in turn, are associated with changes in offspring behaviors, including depressive symptomatology. We know that this cascade from parenting to stress reactivity to brain development exists in rodents, but we don’t know whether this pathway exists in humans. The goal of my dissertation was to examine this link in human children.
To answer this question, I used a longitudinal sample collected by one of my advisors, Dr. Lea Dougherty, and her lab. This sample included offspring of depressed parents and a community comparison group that did not have parental lifetime history of depressive disorders. These children were brought in at 3-5 years-old and asked to complete a parent-child interaction task with their mothers and a task that was designed to make the child mildly stressed (i.e., a laboratory stressor). From these tasks, we were able to measure parenting behaviors and children’s cortisol response to stress. Children and their mothers came back approximately 3 years later and completed another parent-child interaction task to measure parenting behaviors, another laboratory stressor where cortisol was measured, and an MRI session where we collected scans of the structure and function of the child’s hippocampus.
I was particularly interested in whether or not we would see a similar pathway from parenting to stress reactivity to hippocampal structure and function and whether these associations are timing-dependent, meaning that there is a particular age at which these factors have the greatest impact on the brain.
We did find evidence that this pathway may exist in human children. Specifically, we found that greater negative parenting during preschool (3-5 years old), but not middle childhood (5-10 years), predicted greater cortisol reactivity during middle childhood (5-10 years) which, in turn, predicted a smaller size of a particular region of the hippocampus called the tail. This is wholly consistent with what we would predict based on the rodent literature. Although we did not find evidence for this complete pathway when examining the effects of parenting on hippocampal function, we did see that parenting behaviors in both preschool (3-5 years) and middle childhood (5-10 years) were associated with changes in hippocampal networks that have been implicated in the etiology of depressive disorders, including those that are involved in: memory, executive functioning, and rumination. Together, these findings suggest that parenting behaviors throughout childhood may alter the structure and function of the brain and put children at increased risk for depressive disorders later in life.
What is one thing that few people know about this topic, or what is one thing that most people are misinformed about?
Although we do see associations between certain parenting behaviors and the size of certain structures in a child's brain, there are three very important things I like to remind readers of my work: 1) These are not causal associations. We cannot definitively say that certain parenting practices cause changes in a child's brain. Future research may very well disprove these associations or find that they are caused by something that researchers haven't even considered yet. 2) The implications of these differences are yet to be determined. We do not know whether a difference in the size of an area of the hippocampus is good or bad. It's just different. It's possible that these differences may simply amount to different cognitive or socioemotional abilities or make a child more capable of functioning within their environment or it could possibly have no discernable effect on the child’s behavior, cognition, or affect. There is an awful lot we don't know yet about the associations between the size of brain regions and human behavior. The research suggests that it's not a straightforward association and that bigger is not always better and vice versa. 3) Perhaps most importantly, I think it's crucial for everyone (especially parents) to keep in mind that children are incredibly resilient.
How can your research be used by teachers or childcare professionals? How can it be used by parents?
I think this research serves as a good first step towards examining these associations in human children.
Because of the limitations of the present study, such as a small sample size and non-experimental design, I hesitate to make bold claims or recommendations based on this single study at this time. I do believe these findings provide evidence that the rodent literature can help inform human research and that this study (and those that follow) may help us develop more effective early interventions. For example, this research (in conjunction with the replication studies that will hopefully follow) may lead to the development of parenting skills trainings for mothers with high levels of stress or psychological disorders. By elucidating when these parenting experiences have the greatest effect on the development of particular brain systems, future interventions could be targeted to the times when they’ll have the greatest impact on a child’s development.