Research suggests that girls who experience maltreatment may suffer hormonal responses to stress prompting sexual behaviour and resulting in early pregnancy.

During this research, children aged 8-11 were deliberately placed in a stressful situation of giving a short speech to an audience that was trained to be emotionally unresponsive. Hormone levels were monitored before the task and several times for hour afterwards by taking saliva and urine samples.

The results showed that cortisol levels increased among boys following the stressful task, but that there were no significant differences between those who had experienced maltreatment and others. By contrast, while cortisol levels also rose among girls in the control group, this was not the case with those who had experienced abuse.

Maltreated girls released high levels of oxytocin following the task, but there was no significant change among the group girls, or among the boys in either group. Oxytocin levels measured among girls who had been abused were nearly three times higher before the test.

Given the association between oxytocin and positive social behaviour it might seem counter-intuitive that girls with a history of physical abuse would exhibit higher levels than their peers following stress. But the researchers view this as a special case that requires a different way of thinking.

While it could be that the combination of high oxytocin and low cortisol is evidence of damage to the social brain, a more intriguing possibility is that it is “adaptive” — reflecting the increased care-taking role that girls may have played in an abusive family environment and potentially preparing them for early reproduction.

From an evolutionary perspective, early childbearing could have been advantageous for female ancestors exposed to harsh and dangerous living conditions. In a similar way, maltreated girls may respond to their ill treatment with bio-behavioural adaptations geared towards early reproduction.

As a further possibility, higher levels of oxytocin may prompt young women who have been abused to form relationships with men and become sexually active earlier than their peers. The absence of a cortisol response when stressed might equally reflect an adaptive response to repeated early experiences of physical abuse.

The study provides the first evidence that oxytocin levels are higher in maltreated girls approaching full puberty than in other children. It also raises the interesting possibility that young women who have been abused as children are experiencing a hormonal response more appropriate to humankind’s evolutionary past than to modern society.

No firm explanations are yet possible. With understatement, the researchers propose that the precise biological links between early adversity, oxytocin release and stress should be the subject of future research. There is also more to be understood about the differences in stress response between maltreated boys and girls.

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