Abuse in Girls Linked to Abnormal Stress Response

Nancy A. Melville

July 29, 2013

Young girls who have a history of abuse show hormonal responses to stress that contradict normal reactions and may lay the groundwork for dysfunctional relationships later in life, new research shows.

Investigators at the University of Wisconsin–Madison found that young girls who had been physically abused have higher levels of oxytocin and significantly lower levels of cortisol compared with their counterparts who had not experienced abuse.

"Oxytocin in this context may be viewed as the proximate mechanism through which social motivation takes place, with intense family conflict in the form of maltreatment priming females for early departure from the kin group," the authors, led by Leslie Seltzer, PhD, write.

"Such relationships, however, may not necessarily be stable, safe, or developmentally appropriate in modern society," they add.

The study was published online July 19 in Child Development.

Abnormal Stress Response

In the study, 73 children aged 8 to 11 years were exposed to a stress test involving a public speaking challenge with verbal and math components that were to be performed in front of a group of strangers.

Urine samples before and after the challenge showed that the girls with a history of being maltreated not only had higher levels of oxytocin at baseline than any other group but also that after the challenge, they had significantly lower levels of the stress hormone cortisol, which would normally be expected to spike in response to the stress.

Meanwhile, they exhibited higher levels of the hormone oxytocin, which is sometimes called the "cuddle chemical" and is associated more with warmth and affection.

"The fact that oxytocin levels are already higher in maltreated girls at baseline indicates that their much higher oxytocin levels after the [stress challenge] may be indicative not just of dysregulation of the response to acute stress, but of fundamental differences in how their oxytocin system operates," the authors write.

No such differences were observed between abused boys and control boys and girls who had no history of mistreatment.

Sex Differences

Although the reasons why the response was seen only in girls and not boys are unclear, the authors suggested that the high oxytocin levels may be representative either of neurologic dysfunction stemming from the abuse or, conversely, of an adaptive mechanism.

"We're mammals, and in mammals, the females have to gestate, lactate, and [usually] do the lion's share of the childrearing," Dr. Seltzer told Medscape Medical News.

"It's not surprising that girls would have hormonal systems in place that differ from boys', on the basis of this difference in their reproductive demands, even prior to puberty."

The suppression of cortisol and the overexpression of oxytocin suggest a "phenotypic plasticity," or adaptive human behavior, that may logically result from previous exposure to abuse, she added.

"It's possible that the stress and social bonding systems are uniquely intertwined and that repeated exposure to stress increases baseline levels."

"Along the same lines, higher levels of oxytocin facilitate social approach in laboratory animals, so it's possible that girls who have higher oxytocin experience more reward from approaching novel individuals, such as males."

The authors assert that the responses can represent a dangerous hormonal recipe that can make girls vulnerable to the types of behaviors seen all too often among young abuse victims — sexual behavior and the potential for earlier pregnancy.

Reversible?

Commenting on the findings for Medscape Medical News, behavioural scientist Cheryl McCormick, PhD, professor and Canada Research Chair in Neuroscience at Brock University in St. Catharines, Ontario, called the study provocative and interesting, but questioned whether the oxytocin changes could be directly associated with risky behaviors that are common among abused children.

"I think the authors are right in making the point that girls with a history of early childhood stress are more likely to be sexually active earlier and engage in more risky behavior, but the extent to whether that is related to the change in oxytocin is, I think, a bit of a leap," she told Medscape Medical News.

"But it does suggest a way to test for some of those things in animal models, to see if manipulating in the oxytocin system after chronic stress alters behavior in some way."

She added that the changes of blunting cortisol and recruiting oxytocin that were unique to maltreated girls do not necessarily suggest that girls are more capable of adapting to stress than boys but rather that girls simply have a different adaptive mechanism.

"[The observations] just indicate that the girls are differently adapted," Dr. McCormick said.

"The boys could be adapting with some other mechanism. For example, in male rodents, we know that vasopressin plays a very big role in stress responses, so it could be if the authors had looked at vasopressin or testosterone, for instance, they may have seen something different."

"All we can say at this point is there definitely is a change in these girls. We aren't seeing where there has been one in the boys, but there likely is one."

The good news is that evidence indicates that some of the changes that appear linked to abuse or maltreatment in early childhood, or even later, can be reversed, Dr. McCormick added.

"We have seen in data such as studies of children emerging from Romanian orphanages that dysfunction can go away if the children are adopted early enough, so we know that early life stressors can be overcome by a good, stable environment."

Additionally, research is increasingly showing a lot of neuroplasticity in the adolescent period, allowing for recovery well beyond what was previously believed, she said.

"The good news is our brains are more plastic for a longer period than previous thought."

"I think we can abandon the thinking that whatever happened in the first 6 years of life kind of doomed you for the rest of your life. It's really no longer true, and there's lots of evidence supporting recovery in the adolescent period."

The research was supported by a grant from the National Institute of Mental Health. Dr. Seltzer and Dr. McCormick report no relevant financial relationships.

Child Dev. Published online July 19, 2013. Abstract

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