The cognitive, behavioral, and adaptive functioning of 12 men with fragile X syndrome (aged 23 to 62 years) was systematically assessed and compared to two matched groups of retarded men without fragile X syndrome residing at the same institution. The fragile X group was largely indistinguishable from the comparison groups on the cognitive, behavioral, and adaptive measures. Fragile X patients were, however, significantly more likely to have achieved levels of adaptive functioning commensurate with their intellectual abilities. Fragile X subjects who had similarly affected siblings emerged as significantly higher-functioning in all areas than Fragile X subjects who did not have affected siblings. These findings are discussed with respect to future research.
Dykens, E., Leckman, J., Paul, R., & Watson, M. (1988). Cognitive, behavioral, and adaptive functioning in fragile X and non-fragile X retarded men. Journal of Autism and Developmental Disorders, 18(1), 41-52.