"Cocaine readily crosses the placental and fetal brain barriers and has a direct effect on the developing fetal brain …" the authors provide as background information in the article. The authors add that "a number of methodologically sound studies have found a relationship between fetal cocaine exposure and negative child developmental outcomes in the first years of life, although others have not."
In this study, Lynn T. Singer, Ph.D., from Case Western Reserve University, Cleveland, and colleagues assessed the effects of prenatal cocaine exposure and the quality of the caregiving environment on cognitive outcomes. The participants included 376 children (190 cocaine-exposed and 186 non-exposed) from a high-risk population who were enrolled in a longitudinal study from birth (September 1994 – June 1996). They were screened for drug exposure as infants, assessed at 6, 12 and 24 months of age and then tested at 4 years old for cognitive developments.
The researchers found that prenatal cocaine exposure was not related to lower full-scale IQ scores (cocaine exposed 80.7 vs. nonexposed 82.9), summary verbal (cocaine exposed 79.9 vs. nonexposed 81.9) or performance IQ measures (cocaine exposed 85.5 vs. nonexposed 87.5) at age 4 years. "However, there were specific effects of prenatal cocaine exposure on several subscales, with cocaine-exposed children having lower information, arithmetic, and object assembly scores than nonexposed children," the researchers report. "Prenatal cocaine exposure was also associated with a lower likelihood of achievement of IQ above normative means."
The researchers continue, "Comparisons indicated that cocaine-exposed children in foster or adoptive care lived in more stimulating home environments and their caregivers had better vocabulary scores than those of cocaine-exposed children in biological maternal or relative care and nonexposed children. In addition, cocaine-exposed children in foster or adoptive care had verbal, performance, and full-scale IQs equivalent to nonexposed children, while cocaine-exposed children in biological maternal or relative care had lower full-scale and performance IQ scores than nonexposed children, despite the fact that children in foster or adoptive care had twice the severity of cocaine exposure as measured by maternal report of the average numbers of 'rocks' of cocaine used weekly over the pregnancy. Moreover, the duration of placement in foster or adoptive care was positively related to full-scale IQ," the authors note.
"These findings indicate that prenatal cocaine exposure is associated with an increased risk for specific cognitive impairments and a lower likelihood of above average IQ at 4 years of age. In addition, our findings underscore the beneficial effects of environmental intervention in the prevention of mental retardation for cocaine-exposed children. Drug treatment and education for this population of pregnant women, along with intensive intervention for their offspring, are essential to help maximize the future well-being of these families," the authors conclude. (JAMA. 2004;291:2448-2456. Available post-embargo at JAMA.com).
Editor's Note: This study was supported by grants from the National Institute on Drug Abuse and a General Clinical Research Center Grant.