Prenatal Alcohol Exposure and Neurobehavioral Development Where Is the Threshold?

M of the research on pre­ using a variety of assessment instruments from a Seattle cohort of children studied natal alcohol exposure has on children at various ages from infancy by Streissguth and colleagues (1983). focused on the hypothesis to late childhood. These children were born to approxi­ that drinking during preg­ One important issue is the level of mately 5001 predominantly white, middle­ nancy causes structural and biochemical maternal drinking necessary before neuro­ class women in the mid­1970’s. In alterations in the developing brain of the behavioral impairment is seen. Because the contrast, a recent study conducted in fetus. These alterations are thought to body has the ability to tolerate low doses Detroit (Jacobson et al. 1993) examined of most toxic substances, adverse effects affect many aspects of intellectual and 480 economically disadvantaged, black are seen only when exposure exceeds a behavioral function, including attention, infants. In both studies, mothers were certain minimum threshold dose. Severe activity level, and information­processing recruited during pregnancy. All moderate effects of alcohol, such as fetal death, speed. Deficits in these aspects of neuro­ to heavy drinkers and randomly selected mental retardation, and the craniofacial behavioral functions can be measured by lower level drinkers and abstainers were deformities associated with fetal alcohol syndrome (FAS), have relatively high invited to participate (see table 1 for JOSEPH L. JACOBSON, PH.D., is professor thresholds, occurring only in the most drinking levels). of psychology in the psychology depart­ heavily alcohol­exposed fetuses. Sokol The data from these two longitudinal2 ment, Wayne State University, Detroit, and colleagues (1988) estimate that the cohort studies form the basis of this arti­ Michigan. threshold for FAS is consumption by the cle. We describe three types of dose­ mother of approximately 42 standard drinks response relationships reported for SANDRA W. JACOBSON, PH.D., is research (21 ounces of absolute alcohol) per week drinking during pregnancy, introduce professor of psychology in the psychology around the time of conception (table 1). alternative approaches for determining department, Wayne State University, Even at this level, however, not all children threshold values, review data on the Detroit, Michigan. will exhibit FAS (Sokol et al. 1986). thresholds found for neurobehavioral Only a few studies that have focused on The Detroit Prenatal Alcohol Exposure the effects of alcohol on neurobehavioral 1The number of women fluctuated at different phases and Infant Cognition Study was support­ development have investigated thresholds of the study. ed by National Institute on Alcohol Abuse (Jacobson et al. 1993; Streissguth et al. and Alcoholism grants R01–AA06966 1983). Most of the initial data on thresh­ 2Longitudinal studies examine the same group of and P50–AA0706. olds for neurobehavioral effects came people at intervals over time as they age.