Fetal Alcohol Exposure and Attention: Moving beyond ADHD
Coles, Claire D., Alcohol Research
Clinical descriptions of children with feral alcohol syndrome (FAS) and other alcohol-related disabilities (1) often cite attention deficit hyperactivity disorder (ADHD) (American Psychiatric Association [MA] 1994) as a central feature of the behavioral characteristics associated with prenatal exposure to alcohol (Oesrerheld and Wilson 1997). The assumption that prenatal alcohol exposure produces ADHD and other attention problems is based on case study reports and descriptions of patients identified through clinical practice (Steinhausen et al. 1993). The association between prenatal alcohol exposure and ADHD is also supported by results from prospective studies of alcohol-exposed children who do not have FAS (e.g., Streissguth et al. 1995). However, not all empirical studies of alcohol-exposed children have found either the behaviors characteristic of ADHD or deficits on measures of attention on neurocognitive tests (e.g., Boyd et al. 1991; Brown et al. 1991; Fried et al. 1992). These discrepancies, in addit ion to the debate about the ADHD diagnosis itself (see Barkley 1998; Shaywitz et al. 1994), raise a number of questions about the association between ADHD and prenatal alcohol exposure.
The clinical diagnosis of ADHD, although usually reliable, is not based on neurocognitive tests of attention but relies, instead, on clinical observation and on parent and teacher reports. The behaviors measured, therefore, reflect deficits in attention only by inference. In contrast, the methods of neuropsychology and cognitive development use experimental procedures to examine behaviors that reflect the fundamental processes of attention (Mirsky et al. 1991).
To examine the effect of prenatal alcohol exposure on attention factors, as well as the relationship between these factors and the ADHD diagnosis, we (Coles et al. 1997) compared ADHD school-aged children with children diagnosed with either FAS or partial FAS. For this research, we used two sets of criteria.
The first set of criteria was the "traditional" clinical method for diagnosing ADHD using observations of behavior; parent and teacher checklists (e.g., the Child Behavior Checklist [CBCL] [Achenbach 1991] and SNAP [Swanson et al. 1982]); and cognitive tasks typically used by clinicians (e.g., the Wechsler Intelligence Scale for Children, Revised [WISC-R] and Digit Span [Wechsler 1991]). See table 1 for descriptions of these tests.
The second set of criteria was the neuropsychological model developed by Mirsky and colleagues (1991), one of several competing models of attention based on neuropsychological studies. At the time of our study, this model proposed four factors of attention that could be measured using neuropsychological tests. (Another factor has since been added.) The four factors we used were focus, shift, sustain, and encode. Focus refers to the ability to attend selectively to appropriate information. Shift refers to the ability to allocate attentional resources--that is, the ability to shift attention from one task to another when appropriate. Sustain refers to the ability to maintain a focused alertness in perceiving a signal. Encode refers to the ability to maintain information in the working memory while performing some cognitive process using that information (e.g., by manipulating or memorizing symbols). In contrast to the ADHD diagnosis, understanding attention in this manner facilitates the study of both the chara cteristics of attention itself and the differential effects of prenatal alcohol exposure on these more specific factors.
In our (Coles et al. 1997) study, we measured the focus dimension using the WISC-R Coding subtest (Wechsler 1991); the shift dimension with the Wisconsin Card Sorting Test (WCST) (Grant and Berg 1980); the sustain dimension with a computerized vigilance procedure known as the Continuous Performance Test (CPT); and the encode dimension with the Number Recall and Arithmetic subtests from the Kaufman Assessment Battery for Children (K-ABC) (Kaufman and Kaufman 1987). …