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.