Prenatal Cocaine Exposure Leads To Lower Child IQ Scores, Language Skills

October 23, 1998

Prenatal cocaine exposure lowers IQ and language performance scores and results in thousands of children each year who enter school needing special education services, according to a new study by three Brown University researchers.

Up to 80,550 new children will fail in school and need special education services each year at a cost of up to $352 million because they were exposed to cocaine in the womb, said Barry M. Lester, professor of psychiatry and human behavior in the Brown University School of Medicine, and lead author of the study. The study was funded by the Robert Wood Johnson Foundation.

The findings appear in the Oct. 23, 1998, issue of Science, and provide the first systematic glimpse at the long-term effects of prenatal cocaine exposure. Until this point, most studies have involved only infants and preschoolers. "The good news is it gives people room to be optimistic about these kids because the kind of effects we are seeing are treatable with proper intervention," said Lester. "But to do that you've got to believe the money has to be spent."

Researchers analyzed information on more than 800 school-age children from eight studies. Lester worked with Linda L. LaGasse, assistant professor, and Ronald Seifer, associate professor, in the Brown University School of Medicine. Using meta-analysis, a statistical procedure in which studies are pooled, Lester and his colleagues were able to provide a better estimate of the effect of prenatal cocaine exposure than a single study.

Three measures of intelligence were used: IQ, receptive language and expressive language. Receptive language tests measure speaking ability and involve asking a child to identify what is in a picture. Expressive language tests measure comprehension by asking a child to answer questions. Children in the cocaine-exposed group, on average, had IQ scores 3.26 lower than children who were not exposed to the drug. The cocaine effect was even more pronounced with the language tests, which registered twice as large an effect from cocaine exposure as the tests for IQ.

For many people, the difference of three IQ points would be negligible; the average IQ is 100 points. However, that subtle difference must be understood in the context in which cocaine use often occurs, Lester said. Because those children are also likely to live in poverty and other known risk factors that depress IQ scores, the results are dramatic.

To measure the effect on society, the researchers used two statistics for the number of cocaine-exposed children born each year. The National Pregnancy and Health Study estimates that figure at 45,000, based on maternal self-reports. The U.S. General Accounting Office estimates more than 375,000, based on medical records from city hospitals. Both surveys are problematic because of the way information was obtained; the true number is likely somewhere in the middle, Lester said.

Based on those figures, the researchers were able to predict the number of new children who will need special education services annually. Between 1,688 and 37,612 children each year will need special education services because of the IQ difference caused by cocaine exposure. Because those services cost $6,335 per child each year, that means an additional $4 to $80 million in special education costs annually. The cost is even larger for receptive language skills: an additional 4,432 to 80,550 children each year will need special education because of their language skills, at an annual cost of $22 to $352 million.

The subtle effects on intelligence are in sharp contrast to the popular image of hopelessly brain-damaged children of a few years ago. But the effects still mean that money must be spent on prevention, intervention and additional studies, said Lester.

"I don't want the pendulum to swing to the other side," he said. "We started out with hysteria about cocaine devastation, and it would be dangerous for the pendulum to swing to the other side and say the effects aren't there or they are all environmental."

Editors: Lester can be reached at (401) 453-7640.

Brown University

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