For a study, the researchers aimed to compare age- and sex-matched full mutation (FM)-only and pre-mutation (PM)/FM mosaic individuals on intellectual functioning, autism spectrum disorder (ASD) features, and maladaptive behaviors for a study. The researchers comprised a large international cohort of 126 male and female participants with fragile X syndrome (FXS) (1.15 to 43.17 years) separated into FM-only and PM/FM mosaic groups (90 males, 77.8% FM-only; 36 females, 77.8% FM-only). Comparing males and females (FM-only + PM/FM mosaic), males were observed to have poorer intellectual functioning on all domains (P<0.0001). Although females had more minor ASD features and less parent-reported maladaptive behaviors, these differences were no longer significant after controlling for intellectual functioning. , participants with PM/FM mosaicism, regardless of sex, presented with better intellectual functioning and less maladaptive behaviors than their age- and sex-matched FM-only counterparts (P<0.05). ASD features were similar between FM-only and PM/FM mosaics within each sex after controlling for overall intellectual functioning. Males with FXS had reported significantly lower intellectual functioning than females with FXS. However, there were no significant differences in ASD features and maladaptive behaviors after controlling for intellectual functioning, independent of the presence or absence of mosaicism. This suggested to the researchers that interventions that primarily target cognitive abilities may, in turn, reduce the severity of maladaptive behaviors, including ASD features in FXS.