Neurobehavioral phenotype in carriers of the fragile X premutation.

There have been contradictory findings in the fragile X (fraX) literature about possible neurocognitive and psychological symptoms due to the fraX premutation (pM). The purpose of the present study was to investigate the relationship between CGG repeat length and neurobehavioral functioning in carriers of the fraX pM. Eighty-five female carriers of the pM with allele sizes ranging from 59-166 were administered a comprehensive IQ test (WAIS-III) and completed a questionnaire designed to measure psychopathology (Symptom Checklist (SCL)-90-R). No relationship between allele size and cognition was identified. A significant negative relationship between allele size and age was found, as well as a positive relationship between allele size and depression. Follow-up analyses separating small and large allele sizes (below and above 100 CGG repeats) indicated that individuals with larger allele sizes scored significantly higher on the Interpersonal Sensitivity and Depression subscales of the SCL-90-R. Despite the limitation of few individuals with high CGG repeat lengths, our findings suggest that females with larger premutated alleles (> or = 100 repeats) display some clinical manifestations of fraX syndrome. Copyright 2001 Wiley-Liss, Inc.