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Vol. LXIV, No. 13
June 22, 2012

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Experiencing, Observing Abuse Is Linked to Lower Childhood IQ

Severe maltreatment or witnessing domestic violence, especially very early in life, is associated with lower child intelligence, a long-term study has revealed. This cognitive-lowering effect could be as dramatic as lead exposure for young children, according to National Institute of Mental Health-supported scientists at Children’s Hospital Boston.

Many factors can have adverse effects on the budding brain, including malnutrition, medical neglect and physical abuse. While it has been established that childhood trauma can affect multiple measures of cognitive functioning in youth, there is a dearth of information on how exposure to trauma has an impact on the first few years of life.

“Our data suggest that both physical and emotional maltreatment, as well as witnessing violence against the mother, harms a youngster’s brain by impacting the development of cognitive skills,” said Dr. Michelle Bosquet Enlow, lead researcher in the longitudinal investigation.

Dr. Michelle Bosquet Enlow

Dr. Michelle Bosquet Enlow

For this research, more than 200 children in Minnesota, between birth and 5 years of age, were assessed at different stages for exposure to sexual abuse, physical or emotional abuse or neglect and intimate partner violence directed at the mother. The families involved in the study were generally of low income and socioeconomic status. Children were tracked for up to 8 years of age.

Bosquet Enlow and her colleagues used home observations, maternal interviews and questionnaires and assessments of child medical and child protection records to reach the findings. After accounting for factors such as maternal IQ, cognitive stimulation in the home, child gender, race, birth complications and birth weight, the results suggested that trauma exposure had “significant and enduring effects” on cognitive development that were most robust when the exposure occurred between 0 and 24 months of age, a stage when the brain is rapidly maturing.

“We saw an average of a 7-point difference in cognitive scores between those youngsters exposed to maltreatment or violence between birth and 2 years of age and unexposed children,” said Bosquet Enlow. By comparison, she added, “the average lead exposure among children in the U.S. at the time these children were evaluated has been associated with a 6-point decline in IQ scores.” She suggested, “Perhaps we should be treating childhood trauma exposure in the same manner as we treat lead exposure—as a national health issue.”

Post-traumatic stress disorder and anxiety and depressive disorders that can result from trauma exposure may contribute to these processes. For example, heightened feelings of anxiety or withdrawal or intrusive memories of the trauma may interfere with children’s abilities to learn new cognitive skills and achieve academically. “IQ is associated with achievement scores, so in essence, they would be entering school already at a disadvantage,” Bosquet Enlow said.

What happens next? That depends on whether there are existing “buffers”—helpful individuals, programs or mental health treatments tailored to the child’s needs. Supportive people in the environment may include a caring family member or an understanding teacher or therapist, the researcher suggested. However, if youngsters are left untreated, adverse cognitive and emotional consequen-ces could persist well into later childhood and even adulthood.

Results of the investigation appeared in the Apr. 4 online issue of the Journal of Epidemiological Health.

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