By Dr. Jon Caldwell
It may surprise you that some of the most compelling information about human attachment behavior comes from…rodents. These little mammalian mothers form attachment-like bonds with their young pups (i.e., rodent infants) like humans. As it turns out, this bond’s nature profoundly impacts the pup’s development. It has become increasingly clear that the quality of the mother’s care induces numerous biological changes in the pup that can be carried forward into adulthood and the next generation. Thanks to our furry little friends, we now understand some of the mechanisms involved.
What is Attachment Theory?
Attachment theory, pioneered by John Bowlby and Mary Ainsworth in the early 1900s, put forth the idea that the bond between child and caregiver has been naturally selected for by evolution because it offers survival and reproductive advantages. A series of ground-breaking studies showed that children separated from their caregivers experience predictable stages of protest, despair, and detachment. Subsequent attachment researchers, like Alan Sroufe, postulated that early attachment relationships organize the child’s inner world, making them more or less able to negotiate future developmental challenges in middle childhood, adolescence, and adulthood.
By the end of the twentieth century, attachment theory had become prominent in psychology. Yet, little was known about the biological mechanisms responsible for most of its basic tenets. That began to change with fascinating research in mice and rats, like that of Marion Hofer and his colleagues. They recognized that, like human infants, rat pups experienced similar stages of protest and despair when separated from their caregiver. More importantly, they found that caregiver separation during specific periods of development (usually in the first two weeks) resulted in several physiological deficits in the rat pups.
The Impact of Caregiving on Development: Attachment Theory
Hofer and his colleagues discovered that specific maternal caregiving behaviors were related to the development of specific biophysiological processes in the rat pups during critical periods. For example, if pups were not allowed to receive body-to-body warmth and closeness from their caregiver, they developed specific deficits in their ability to regulate their activity level (e.g., they were more lethargic, hypoaroused). On the other hand, if the pups received caregiver warmth but did not receive a continuous infusion of maternal milk, they could not regulate their heart rate (but their activity level was normal). These researchers concluded that the caregiver-infant relationship contained “hidden regulators” that fundamentally shaped the infant’s biophysiology.
Around the turn of the twenty-first century, there was incredible excitement about the promise of the human (and rodent) genome project. Gradually, it became clear that simple one-gene-to-one-disease models were overly simplistic and that most conditions were a product of complex interactions between genes and the environment.
With this in mind, researchers like Michael Meaney extended the work of Hofer and others into a new dimension of epigenetics research. Epigenetics refers to the somewhat radical idea that while our inherited genetic code remains fairly stable throughout the lifespan, the quantity and quality of protein products made from the genetic code are highly variable and heavily influenced by the environment. That is to say, the expression of the genetic code (i.e., which genes are turned on/off, in which parts of the body, and at what times) is influenced by various environmental factors.
Understanding the Biological Mechanisms of Attachment Theory
A simple laboratory observation kick-started Michael Meaney’s elegant line of research that rat pups handled by humans tended to develop into less anxious and less fearful adults. Fortunately, they overcame the species-centric urge to attribute the positive results to human contact and discovered that pups that were handled by humans received more grooming from their mother. (Rat mothers were dutifully cleansing their pups of human contact!) This led to the exciting discovery that the maternal rat’s licking and grooming behavior was responsible for their well-adjusted offspring.
Meaney and his colleagues found that high-quality maternal care in rats involves licking and grooming behavior and a style of nursing where the mother’s back is highly arched. They also discovered natural variations in the quality of maternal care – some maternal rats were quite good at arched-back nursing and licking/grooming behavior, while others were not. This led to the discovery that pups who received high levels of maternal care (arched-back nursing and licking/grooming) were less anxious as adults, more willing to explore their environment, and they became mothers who delivered high levels of maternal care to their own offspring.
Of note, these researchers wanted to be sure that the outcomes associated with high-quality maternal care were not simply due to inherited genes. So, they took pups from low-quality caregiving mothers and gave them to high-quality caregiving mothers (cross-fostering), and vice versa. The results showed that the quality of caregiving determined the positive outcomes, not the pup’s genetics.
Now, these researchers had an animal model that looked much like what we see in humans: high-quality maternal care (i.e., attachment security) organizes developmental processes to support greater well-being and caregiving advantages for the subsequent generation. These researchers were poised to answer the next burning question: What are the underlying biological mechanisms?
The Effects of Maternal Care on Epigenetic Programming
This is where epigenetics re-enter the story! Meaney and his colleagues discovered that during sensitive periods of development (the first week of life for rats), high-quality maternal care stimulates (i.e., turns on) the expression of a gene that codes for a protein called glucocorticoid receptor (GR). The GR gene becomes more active because the mother’s licking and grooming behavior set in motion a cascade of chemical messengers in the pup that eventually act on specific epigenetic factors (e.g., histones and methyl groups) that alter the shape of the DNA, making it more accessible for genetic expression.
As is common in epigenetics, the maternal rat’s high-quality caregiving behavior stimulates GR gene expression in the pup at specific locations within the body: in this case, a brain region called the hippocampus. This is critically important because the hippocampus generates the body’s fight-or-flight reaction to stress. When more glucocorticoid receptors are present in the hippocampus, the fight/flight response is attenuated. Therefore, high-quality maternal care alters the GR gene’s shape, increasing GR gene expression and glucocorticoid receptors in the pup’s hippocampus. This results in a rat pup with better nervous system regulation that behaves more calmly and confidently as an adult.
Although epigenetic programming by maternal care occurs during sensitive periods early in life and tends to be stable over the lifespan, there is evidence that these effects can be reversed. Even as adults, these same epigenetic processes remain open to environmental influences and can potentially be harnessed for the purpose of change. There is some evidence that consistent and repetitive activation of certain brain circuits might induce epigenetic modifications, leading to stable changes in gene expression. Ultimately, changes in gene expression modulate complicated neurochemical feedback loops, which alter neurobiological systems’ structure and function.
Thus, there is a real possibility that future research will help identify ways that specific environmental factors, including the environment of our mind, can be utilized to access these powerful epigenetic processes. We will probably still talk about mice and mothers in that wonderfully hopeful time.
Potential Solutions for Providing Higher Quality Maternal Care
Improving access to healthcare is essential for providing quality maternal care. Without access to healthcare, mothers may be unable to receive the medical attention and guidance needed to ensure the health of their offspring. Furthermore, healthcare providers have an important role in educating mothers on the importance of maternal care and providing advice and guidance on caring for their offspring properly.
Increasing awareness of maternal care is also important for providing quality care to offspring. Educating parents and caregivers on the importance of maternal care and offering resources and support can help them to provide the best care possible. This could include providing information on the various ways to provide quality care, such as providing adequate nutrition, interacting and responding to their offspring, and providing a supportive and nurturing environment.
Finally, providing more support and resources to caregivers is essential for ensuring they have the tools to provide quality care. This could include offering support through counseling and parenting classes and providing resources such as books and videos on proper maternal care. Additionally, providing financial assistance to caregivers can help to reduce the stress and strain associated with providing proper care.
By taking these steps, we can help to ensure that all caregivers have the resources and support needed to provide quality maternal care and ensure the health and development of their offspring.
The Quality of Maternal Care Impacts Offspring Development
Maternal care is essential for proper offspring development, both physically and psychologically. Studies have found that the quality of maternal care provided to offspring shapes its development, with offspring born to a mother with high-quality care more developed than those born to mothers with low-quality care. This has been found in mice and humans and highlights the importance of providing quality maternal care to ensure proper offspring development. Solutions such as improving access to healthcare, increasing awareness of maternal care, and providing more support and resources to caregivers can help improve the quality of maternal care and ensure the well-being of offspring.
Raising awareness about its importance is one of the most important steps in improving maternal care. Education about the impact of maternal care on a child’s development should be made more accessible through community centers, schools, or online resources.
Additionally, if needed, caregivers should be provided more support and resources, such as childcare and mental health services. Governments should also invest more in healthcare and other services that can help provide quality care to children. Finally, a culture of understanding and acceptance towards parents should be cultivated to reduce the stigma of asking for help and encourage more parents to seek aid when needed. These initiatives are key in improving the quality of maternal care and, ultimately, the development of our children.
About Jon G. Caldwell, D.O.
Jon G. Caldwell, D.O., is a board-certified psychiatrist treating adults with relational trauma histories and addictive behaviors. Dr. Caldwell works full-time as a psychiatrist at The Meadows treatment center in Wickenburg, Arizona. For many years, he has taught students, interns, residents, and professionals in medicine and mental health about how childhood adversity influences health and well-being. His Ph.D. graduate work heavily influences his theoretical perspective at the University of California at Davis. He has been researching how early childhood maltreatment and insecure attachment relationships affect cognitive, emotional, and social functioning later in life. Dr. Caldwell’s clinical approach has become increasingly flavored by the timeless teachings of contemplative traditions and mindfulness meditation.