Effortful control, or the ability to suppress a dominant response to perform a subdominant response, is an early-emerging temperament trait that is linked with positive social-emotional development. Fragile X syndrome (FXS) is a single-gene disorder characterized by hallmark regulatory impairments, suggesting diminished effortful control. This…

This study compared the developmental status, functional abilities, and temperaments of 31 young (36 to 95 months) boys with fragile X syndrome (FXS) who did not have autism, matched on chronological age, gender, and race, with 31 boys with autism but no FXS. Overall, the boys with autism exhibited a more variable profile of development than did…

This study examined whether the variability in development in fragile X syndrome is related to FMR protein deficiency in 53 young males with various degrees of the syndrome. FMR protein expression accounted for a small but significant amount of variance in level, but not rate, of development. Findings support the hypothesized relationship but…

A study of 57 boys with fragile X syndrome (ages 24-133 months) assessed the extent to which autism and autistic features were evident using the Childhood Autism Rating Scale (CARS). Fourteen subjects scored above the cut-off for autism, with 12 of the 14 in the mildly or moderately autistic range. (Author/CR)

Adaptive behavior was measured over time in 70 children, ages 1 to 12 years, with fragile X syndrome. With a mean of 4.4 assessments per child, adaptive behavior skills increased steadily and gradually over time. Children with less autistic behavior and higher percentages of the fragile X mental retardation gene protein showed better performance…