A study focusing on the role of a important brain chemical sheds new light on why victims of childhood abuse may themselves become abusers as adults, and points to a possible remedy, researchers said on Thursday.
They looked at levels of serotonin — a chemical that transmits impulses in the brain — in rhesus monkeys, but has implications for understanding child abuse in people because of biological similarities in humans and monkeys, they said.
When baby monkeys in the study experienced high amounts of abuse and rejection from their mother in the month after birth, their brains often produced less serotonin. Low levels of serotonin are linked to anxiety, depression and aggression in monkeys and people.
The researchers followed monkey infants from birth into adulthood. They found that female monkeys that had been abused by their mothers as infants and later became abusive mothers had about 10 to 20 percent less serotonin than females that had been abused as babies but did not become abusive parents.
Understanding the cycle
Experts long have known that suffering childhood abuse raises the probability a person will become an abusive parent, and have tried to find the reason — for example, repeating behavior learned early in life or, alternatively, long-term changes in brain processes governing emotions.
"Our results suggest that the system is affected by early trauma, early experience, and that these long-term changes in the brain might contribute to the occurrence of abusive parenting in adulthood," University of Chicago researcher Dario Maestripieri said in an interview.
Maestripieri, lead author of the study in the journal Behavioral Neuroscience, said if research confirms that the same changes in brain development also occur in humans, then there could be the potential for intervention using drugs.
Maestripieri said drugs that raise brain serotonin levels might lower the chances an abused child becomes an abusive parent.
The team watched mothers as they parented to note hitting and other negative behaviors toward their infants. They swapped monkey infants at birth between different mothers to determine that the observed changes did not merely reflect genetic similarities between babies and their mothers.
"I think we've made another step forward in understanding exactly how early experience affects this inter-generational transmission of abuse," Maestripieri added.
The abuse included having the mother grab babies by the leg or tail, step on them, pin them down or throw them in the air, Maestripieri said. The study did not look at paternal abuse because it involved a monkey species whose parental care is entirely performed by females, he said.