The absence of a loving caregiver in the earliest years of life could sway the normal activity of two hormones - vasopressin and oxytocin - that play an essential role in the ability to form healthy social bonds and emotional intimacy.
Announced by psychologists at the University of Wisconsin-Madison, the new finding demonstrates for the first time that severe neglect and social isolation can directly affect a young child's neurobiology in ways that potentially influence emotional behaviors. The work is reported online in the Nov. 21, 2005 Proceedings of the National Academy of Sciences.
"Questions about how children regulate emotions and form social bonds has not really made contact with recent advances in the neurosciences," says senior author Seth Pollak, a UW-Madison professor of psychology, psychiatry and pediatrics and researcher at the Waisman Center for Human Development. "But this work makes a link between complex emotional behaviors and the developing brain."
"It's exciting that we've taken an area of child development that has been very descriptive and can now look at it in a more mechanistic way," adds doctoral student Alison Wismer Fries, the lead author of the study.
The UW-Madison work emerges at a time when families in the developed world are adopting children internationally in record numbers. Orphanages in developing nations, however, are often overwhelmed by the numbers of children in their care. Many adopted children who lived in such orphanages, consequently, spent some part of their early years without the emotional and physical contact that is so critical for social development.
Crucial to making the link between social behavior and hormones was the work of co-author Toni Ziegler, an endocrinologist at the UW-Madison National Primate Research Center, who developed a technique that enables researchers to track vasopressin and oxytocin levels through the analysis of urine. The procedure is far less invasive than the existing method of analyzing blood or cerebrospinal fluid, and may one day find applications in several areas of child research such as the field of autism, Ziegler says.
The UW-Madison scientists worked with 18 four-year-old children who had lived in Russian and Romanian orphanages before being adopted into homes in the Milwaukee area. Despite the fact that the children now live in stable homes - for over three years, in some cases - they might still display some of the telltale behaviors that researchers have come to associate with early neglect. The abnormal willingness of a child to seek comfort from unfamiliar adults, even in the presence of the adopted parent, is one common instance of such behavior, says Wismer Fries.
Before starting her experiment, Wismer Fries collected urine samples from the young subjects to track baseline levels of vasopressin and oxytocin. Immediately, the scientists noticed that the children who experienced early neglect had markedly lower levels of vasopressin than the control group of non-adopted children. Researchers believe that vasopressin is essential for recognizing individuals in a familiar social environment. Lower levels of the hormone, Pollak says, may point to the social deprivation these children endured early on.
During the experiment, study subjects sat on the laps of either their mother or an unfamiliar woman and participated in an animated interactive computer game. The 30-minute game directed the children to engage in various types of physical contact with the adult they were sitting with, such as whispering or tickling each other, and patting each other on the head. When the game ended, Wismer Fries collected another urine sample from each child.
The UW-Madison researchers expected to see a hormonal response in the children following the physical contact with their mothers. And predictably, oxytocin levels rose in family-reared subjects. Yet, levels stayed the same among the previously neglected group. That result may help explain the difficulties many of these children have in forming secure relationships, the UW-Madison scientists say.
What is important to note, Pollak points out, is that the study results do not suggest that victims of early neglect are biologically barred from forming healthy relationships later in life. "It's extremely important that people don't think this work implies that these children are somehow permanently delayed," says Pollak. "All we are saying is that in the case of some social problems, here is a window into understanding the biological basis for why they happen and how we might design treatments."
In the future, Pollak and Wismer Fries hope to identify how particular factors, such as the duration or severity of childhood neglect, might influence types of child behavior. Why hormone levels vary between children who've suffered similar neglect patterns is another potential area of exploration.
High-resolution images are available for downloading at: http://www.news.wisc.edu/newsphotos/bonding.html
Alison Wismer Fries
Proceedings of the National Academy of Sciences