The Wechsler Abbreviated Scale of Intelligence is a reliable and valid measure of intellectual functioning in children and adults.
An estimation of present intelligence (IQ) as an overall measure of intellectual functioning was derived from the information, similarities, block design, and picture completion subtests of the Wechsler Adult Intelligence Scale (WAIS) [ 20, 70].
Furthermore, although global measures of intellectual functioning have proven to be sensitive measures of exposure to a number of environmental chemicals, this has not been the case for prenatal exposure to alcohol or drugs (NIDA 2000).
All patients and control subjects underwent standardized cognitive assessments including measures of intellectual functioning, IQ (Nelson and O'Connell, 1978; Wechsler, 1997) and measures of verbal learning and design learning (Coughlan et al., 2007) previously demonstrated to be sensitive to the integrity of temporal structures (Baxendale et al., 2006) (Table 1).
Numerous studies of children have shown that lead exposure reduces overall cognitive functioning in children, both cross-sectionally and longitudinally, but most such studies examine omnibus measures of intellectual functioning rather than domain-specific effects [ 35, 42– 42].
Although the concentrations of the two elements were correlated (Spearman r = 0.36), exposure to As, as measured by water, urine, and blood concentrations, was essentially negligible, and none of the measures of As exposure was associated with any measure of intellectual function.
The present study improves on previous studies by including a measure of intellectual function from a standardized test (WISC-III) [ 16] and measures of mental health from a validated clinical interview generating DSM-IV diagnoses (Kiddie-SADS-PL) [ 17] and a general function score (the Children's Global Assessment Scale) [ 18].
Also, the standard deviations for the various measures of intellectual function show very similar standard deviations in our samples at 6 and 10 years of age, so that it does not appear that there is substantially more measurement "noise" in the younger sample.
The FSIQ z-score was used to measure overall general intellectual functioning ("Intelligence" domain).
