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Date: Wednesday, May 15, 1996 FOR IMMEDIATE RELEASE Contact: NICHD, Birgit An der Lan (301)493-4541
Infants who were prenatally exposed to cocaine may be more affected emotionally than intellectually, according to collaborating teams of pediatricians and psychologists from the Yale Child Study Center, led by Linda Mayes, and from the National Institute of Child Health and Human Development (NICHD), led by Marc Bornstein. As infants, these children tend to be very easily overstimulated and distressed by unfamiliar sights and sounds, but their ability to process information may not be as affected.
It is estimated that at least 50,000 and perhaps as many as 375,000 infants are born yearly in the United States to mothers who abuse cocaine or crack while pregnant. The investigators are studying the impact of cocaine on the mental and emotional development of these babies.
The work is described in several reports, the most recent of which appears in the current issue of Development and Psychopathology, which is devoted to and entitled "Regulatory Processes in Development." This article describes how researchers, who recruited women at Yale-New Haven Hospital, recorded the emotional reactions of 63 infants when they were presented with pictures of unfamiliar faces or objects. The mothers of 36 of these infants had used cocaine during pregnancy, and their babies' reactions were compared with those of 27 non- exposed infants from a similar socio-economic background. The researchers conclude that cocaine exposed babies are more likely to respond to such novel images by fretting or crying than are children who are not exposed to cocaine prenatally. In fact, some of the cocaine babies were so irritable that they couldn't be tested.
Long before children can talk, their intellectual abilities can be gauged by measuring how long something holds their attention. Typically, if an infant is presented with an image, he or she will look at it for a while and then pay less and less attention to it. The decline in attention is termed "habituation," and measuring it has revealed a great deal about such aspects of infants' mental abilities as memory, color discrimination, and perception of pattern and symmetry. Much of this work was carried out by Marc Bornstein. An experimenter can, for example, find out whether babies can group people by gender by showing several pictures of male faces and then one of a female face. If the baby gets bored with the male faces, and then shows renewed interest when presented with a picture of a female face, researchers would infer that the baby could distinguish male from female. To test memory, the original image can be shown again after a lapse of time. If as much time is devoted to it as on first viewing, i.e., it is treated as "new", researchers would conclude that the infant had not remembered, whereas a shorter attention time would suggest recognition of the image.
Prenatal cocaine exposure was found not to alter the rate at which infants habituate to a novel stimulus, leading the researchers to conclude that information processing per se may not be affected by cocaine. The tests of information processing, which were performed on a total of 108 three-month-old infants, were described in the journal Pediatrics last year (April issue). Physiologically, cocaine seems to act both directly on the brain and on the placental/fetal blood supply. In lower brain centers important for regulating attention and arousal, cocaine inhibits the re-uptake of a certain class of neurotransmitters, leaving the space between nerve cells awash in these mood-altering substances (dopamine, norepinephrine, and serotonin) and resulting in overstimulation of the corresponding nerve pathways. Cocaine also constricts blood vessels both in the placenta and in the fetus itself, starving the fetus of oxygen and thus compromising fetal neurodevelopment.
The Yale/NICHD teams believe that irritability and oversensitivity to novelty have several important implications for the development of cocaine-exposed infants. Firstly, adults the world over, says Dr. Bornstein, in addition to comforting, often respond to crying infants by distracting them. This
strategy is likely to make matters worse for cocaine-exposed babies. Secondly, a fretful, fussy baby is harder to care for and respond to, a problem that is compounded by the fact that these babies are not only born to but are often also reared by substance- abusing mothers, whose addiction impairs their ability to interact with their infants.
Furthermore, oversensitivity to novelty is also likely to undermine a child's ability to explore and to learn, which may give rise to the impression that the child has a cognitive impairment. This may lead teachers and others to offer inappropriate remediation to these children, whose excitability threshold has been lowered by their cocaine exposure; teaching programs for these children should therefore be designed to minimize overstimulation.
The NICHD is part of the National Institutes of Health, the biomedical research arm of the Federal government. Since its inception in 1962, the Institute has become a world leader in promoting research on development before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation.