Cognitive and Social-Emotional Development in Girls With Fragile X Syndrome.

Objectives: To evaluate the developmental trajectory of key cognitive, social, and emotional features in girls with fragile X syndrome (FXS).

Methods: This longitudinal, parallel cohort study collected data between January 2018 and December 2022. Participants were evaluated 3 times with ∼12-18 months between visits. Participants included 65 girls with FXS, 6 to 16 years, and 52 age- and developmentally-matched girls without FXS. Participants' scores from direct assessment and caregiver report evaluated 3 cognitive domains (verbal abilities, nonverbal abilities, executive function) and 4 social-emotional domains (depression, general anxiety, social behavior, and social anxiety).

Results: Participants included 117 girls (mean [M] [SD] age at study entry: FXS M = 10.59 [3.00]; comparison M = 10.45 [2.40])). Omnibus tests showed 4 domains with significant group differences: Verbal (P < .0001, eg, Differential Abilities Scale-II(DAS-II), Picture Vocabulary (-6.25 [1.87])), nonverbal (P < .0001, eg, Kaufman Test of Educational Achievement, Third Edition, Brief Form, Math (-8.56 [2.90])), executive function (P < .0001, eg, NIH Toolbox List Sorting (-6.26 [1.48])), and social anxiety (P < .03, eg, Anxiety, Depression, and Mood Scale (ADAMS) Social Avoidance (1.50 [0.65])). Three domains had significant group by age interaction: Verbal (P < .04, eg, DAS-II, Word Definitions (-1.33 [0.55])), social behavior (P < .01, eg, Social Responsiveness Scale-2 Social Communication (1.57 [0.51])), and social anxiety (P < .01, eg, ADAMS Social Avoidance (0.46 [0.19])).

Conclusions: These findings support the development of early, disorder specific interventions for girls with FXS targeting verbal and nonverbal skills, executive function, social behavior, and social anxiety.