Cognitive profiles of the carrier fragile X woman.

Cognitive deficits in females with fragile X [fra(X)] syndrome have been reported, but studies have rarely focused on women with normal intelligence, nor have they separated fra(X)-negative carriers from fra(X)-positive carriers. Questions specifically addressed here are: 1) is the degree of fragility predictive of IQ? 2) are cognitive patterns consistent across fragility levels? and 3) do consistent individual profiles exist? These questions were addressed with the help of 74 heterozygous women, 38 of whom were fra(X)-negative carriers. All women completed the WAIS-R, and full-scale IQ was normally distributed (mean = 99.65). A strong inverse relationship between IQ and fragility levels was found. Also, the group of fra(X)-positive women had a significantly different subtest pattern from that of the fra(X)-negative women. However, when results were analyzed individually, no consistent patterns emerged. The cognitive performance of fra(X)-negative carriers has probably been underestimated due to the lack of differentiation between positive and negative carrier females in previous studies. These women appear to be cognitively unimpaired and should be considered separately from fra(X)-positive women. Since consistent WAIS-R patterns are not observable on an individual basis, their use as a diagnostic/predictive tool appears to be inappropriate.