Trajectory of adaptive behavior in males with fragile X syndrome.

Adaptive behavior in males with fragile X syndrome was longitudinally examined in 17 subjects, ages 1 to 17. Subjects received adaptive behavior evaluations on two occasions within one of three age periods. All domains of the Vineland Adaptive Behavior Scales increased from youngest to oldest age groups, yet older subjects (ages 10 to 17) showed significant declines in their adaptive behavior scores from first to second testing. A relative strength in Daily Living Skills and weakness in Socialization emerged only among older subjects. There was a significant relationship between adaptive behavior and mental age scores in all subjects. Discussion emphasized the parallels between declines in IQ and adaptive behavior as well as the need for further research on adaptive skills in young adults with fragile X syndrome.