Teratogenic effects of Alcohol on brain and behavior

Alcohol Research & Health,  Fall, 2001  by Sarah N. Mattson,  Amy M. Schoenfeld,  Edward P. Riley

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Children prenatally exposed to alcohol can suffer from serious cognitive deficits and behavioral problems as well as from alcohol-related changes in brain structure. Neuropsychological studies have identified deficits in learning and memory as well as in executive functioning both in children with fetal alcohol syndrome and in children with less severe impairments. Both groups of children also exhibit problem behaviors, such as alcohol and drug use, hyperactivity, impulsivity, and poor socialization and communication skills. Brain imaging studies have identified structural changes in various brain regions of these children--including the basal ganglia, corpus callosum, cerebellum, and hippocampus--that may account for the cognitive deficits. Functional brain imaging studies also have detected changes in alcohol-exposed children indicative of deficits in information processing and memory tasks. KEY WORDS: fetal alcohol syndrome; prenatal alcohol exposure; teratogenesis; brain imaging; neuropsychological assess ment; cognitive and memory disorder; basal ganglia; corpus callosum; cerebellum; hippocampus; electroencephalography; magnetic resonance imaging; positron emission tomography; single photon emission computed tomography

Prenatal alcohol exposure can have serious and permanent adverse effects on children. The extent and severity of a child's condition depends on several factors, such as how much alcohol the pregnant mother consumed and how often and at what point during her pregnancy she drank. The most serious outcome is feral alcohol syndrome (FAS), the diagnosis of which is based on three criteria: (1) growth deficiency manifested by small overall height and small head size (i.e., microcephaly); (2) central nervous system disorders; and (3) a distinctive pattern of abnormal facial features. Other children with histories of heavy prenatal alcohol exposure, however, often do not meet the diagnostic criteria of FAS. These children, who typically lack the characteristic facial features of FAS, have variously been labeled as having fetal alcohol effects (FAE), alcohol-related neurodevelopmenral disorder (ARND), or prenatal exposure to alcohol (PEA). Both children with FAS and those with related disorders can be born to women kn own to drink in a heavy episodic fashion or more regularly during pregnancy. For the remainder of this article, children with histories of prenatal alcohol exposure who do not meet the diagnostic criteria of FAS are referred to as either having FAE or PEA. When available, data from such children are noted; otherwise, the results presented in this article refer to children diagnosed with FAS.

Children with histories of heavy prenatal alcohol exposure show evidence of changes in brain structure and function as well as a variety of behavioral effects presumably resulting from this insult to the brain. Most of the research conducted among alcohol-exposed children and adolescents has focused on either the structural or behavioral effects. Only recently have studies begun to demonstrate the relationship between the two areas--that changes in brain structure could negatively affect behavior. This article summarizes the results of neuropsychological studies analyzing alcohol's teratogenic (i.e., damaging to the developing fetus) effects on behavior and of brain imaging studies analyzing alcohol's effects on brain structure. It then highlights the existing connections between those two areas of research. For more extensive coverage of these topics, the reader is referred to review articles by Mattson and Riley (1998) and Roebuck and colleagues (1998).

RESULTS FROM NEUROPSYCHOLOGICAL STUDIES

Generally, heavy prenatal alcohol exposure is associated with deficits in a wide range of areas of function, including both cognitive functioning (e.g., general intellectual functioning, learning of new verbal information, and performance on visual-spatial tasks) and fine- and gross-motor performance. Neuropsychological studies have analyzed the cognitive impairment of children with histories of prenatal alcohol exposure. Although many of these studies have focused on children diagnosed with FAS, several analyses have included children with FAE or PEA.

Importantly, many studies show that strong similarities exist between children with FAS and children with FAE/PEA. For example, studies of overall cognitive ability in FAS children typically report average IQ scores in the borderline range of functioning (i.e., in the low 70s), although they can range from "intellectually deficient" (IQ scores less than 70) to "average" (IQ scores between 90 and 109). Children with FAE or PEA also show deficits in IQ scores, although these deficits typically are not as severe as in the children with FAS (Streissguth et al. 1991; Mattson et al. 1997).

In addition to overall intellectual or cognitive deficits, researchers have evaluated a broad range of cognitive functioning areas in children with FAS, FAE, or PEA, including language skills, visual-spatial functioning, fine-motor behavior, nonverbal learning, and academic performance. In general, alcohol-exposed children both with and without FAS show significant impairments in all neuropsychological areas with few qualitative differences observed between the FAS and PEA/FAE groups. Similarly, high levels of prenatal alcohol exposure are related to an increased risk for cognitive deficits across a range of functioning areas, which again can occur in children both with and without a diagnosis of FAS.