Cocaine Exposure Dooms Infants, Study Says

The study finds that rat fetuses exposed to cocaine levels comparable to daily recreational use in humans show lasting dysfunction specifically in the area of attention. Researcher Barbara J. Strupp, associate professor of psychology and of nutritional sciences at Cornell, says the findings can be applied to humans.

"Although prenatal cocaine exposure does not seem to affect most areas of cognitive function, the deficits in attention are consistent and lasting -- seen in adult animals long past the period of exposure. In humans, this type of dysfunction could significantly impact the lives of affected children, as seen in cases of attention deficit hyperactivity disorder (ADHD)," says Strupp, co-author of a study on prenatal cocaine exposure to be published in Behavioral Neuroscience in August.

"There appear to be some differences between the cognitive profile seen in these cocaine-exposed animals compared to that of ADHD, but in both cases, attentional dysfunction is prominent while many other cognitive processes are unaffected," she says. "However, perhaps it should be noted that even though the effects of prenatal cocaine exposure are likely to be significant, they do not support the devastation implied by media reports of the early 1990s.

"Researchers have become increasingly concerned about the effects of cocaine use during pregnancy because of the growing incidence of cocaine-exposed babies. This increased incidence is due to the advent of crack cocaine, a cheaper form of cocaine that is being used increasingly by poor and young pregnant women," says Strupp.

A National Institute of Drug Abuse survey published in 1996 estimated that 1.1 percent of pregnant women in the United States -- 45,100 women -- smoke crack cocaine each year. A 1998 Yale University study found that the incidence of prenatal cocaine exposure in infants seeking medical care primarily through an emergency service might be as high as 1 in 3 to 6 infants in a predominantly inner-city population. Yet, researchers find it difficult to isolate the specific effects of prenatal exposure to the drug in children because of confounding factors such as prenatal undernutrition, maternal stress, prenatal and postnatal medical care and accompanying exposure to alcohol, nicotine, marijuana, opiates and amphetamines.

In Strupp's study, the researchers surgically implanted catheters into pregnant rats, half receiving doses of cocaine comparable to human "recreational doses" and half receiving a harmless saline solution. Offspring then went through a series of cognitive tasks. The prenatal cocaine did not affect the offspring in areas such as basic learning ability, short- and long-term memory (both implicit and explicit), impulse control and cognitive and behavioral flexibility, among others.

However, the researchers found that prenatal cocaine produced its most significant effect on selective attention in rats -- the ability to stay focused despite environmental distractions. Attention in these animals seemed to be "captured" by the strongest cues in the environment, Strupp explains.

"When the most salient cues were needed to perform a task, then the performance of the cocaine-exposed animals did not differ from controls. But when the most salient cues were irrelevant or distracters, the cocaine-exposed animals were significantly impaired in performing the tasks. This type of deficit could have serious effects on the school performance of affected children," Strupp says.

The study was supported, in part, by the National Institute of Drug Abuse and the National Institute of Environmental Health Sciences.