Developmental trajectories of executive functions in young males with fragile X syndrome.
Boys with FXS keep lagging in EF, yet they inch forward each year—track the inches, not just the gap.
01Research in Context
What this study did
Cohen et al. (2018) tracked the same group of boys with fragile X syndrome for five years. They gave each boy the same set of executive-function games every year.
Scores were compared to kids who had the same mental age but not FXS. This let the team see if FXS boys stayed behind, caught up, or fell further back.
What they found
Across every visit, boys with FXS scored lower than their mental-age peers on all EF tasks. The gap never closed.
Yet the boys did not stand still. Their raw scores crept upward year after year, showing slow but real growth.
How this fits with other research
Sutton et al. (2022) pooled 26 studies and found the same small, steady EF lag across all intellectual disabilities. The FXS data line up with that big picture.
Onnivello et al. (2024) saw a matching pattern in Down syndrome: age-equivalent scores rose while standard scores dropped. Both syndromes share the ‘real growth, relative loss’ curve.
Finney et al. (1995) claimed no syndrome-specific profile once IQ drops below 40. R’s FXS-only tracking now shows EF growth speed does differ by syndrome, adding nuance to the older view.
Why it matters
For your FXS clients, expect EF skills to stay behind mental-age peers, but watch for tiny yearly gains. Use those inches: set goals just above last year’s score, not at mental-age level. Repeat probes each annual review—slow growth is still growth you can leverage.
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02At a glance
03Original abstract
BACKGROUND: Executive functions (EF) have been identified as impaired in FXS, but few studies have examined their developmental trajectories. AIMS: The primary aim of this longitudinal study was to examine the development of EF in young males with FXS compared to Mental Age (MA)-matched controls. METHODS AND PROCEDURES: The sample comprised 56 boys with FXS (ages 7-13 years), and 48 MA-matched typical boys (ages 4-8 years). EF tasks included measures of inhibitory control, working memory, cognitive flexibility/set-shifting, problem solving/planning, and processing speed. Tasks were administered at three time points over five-years. OUTCOMES AND RESULTS: The MA-Matched Typical boys significantly outperformed the FXS boys on all EF tasks, with the FXS Group showing a pattern of slow, but positive growth on most EF tasks. For working memory tasks, significant interactions were noted between MA and autism symptom severity, and MA and medication status. The probability of task completion increased with higher MA. CONCLUSIONS AND IMPLICATIONS: These findings contribute to our understanding of the development of EF in this population. They also lay the foundation for use of EF tasks in treatment efforts, particularly with respect to documenting improvements and practice effects, and in understanding associations with targeted developmental outcomes.
Research in developmental disabilities, 2018 · doi:10.1016/j.ridd.2018.05.014