Background. People with fragile X syndrome (FXS) often experience co-occurring anxiety and autism; however, characterising and distinguishing anxiety is challenging due to overlap with autistic characteristics. Autism characteristics, such as sensory sensitivities and restricted/repetitive behaviours (RRBs), are common in FXS and may be associated with an increased likelihood of anxiety. Furthermore, studies indicate that intolerance of uncertainty (IU) may serve as a risk factor for the development and maintenance of anxiety and may mediate the relationship between anxiety and autism characteristics for autistic individuals. Characterising the relationship between autism characteristics, IU, and anxiety is essential to informing anxiety interventions and theoretical models for people with FXS. This study investigates the relationship between sensory sensitivities, RRBs, IU, and anxiety in people with FXS (n = 26, Mage = 28.08 years). 

Methods. Parent-reported sensory sensitivities, RRBs, and IU were assessed using the Sensory Experiences Questionnaire (SEQ), Repetitive Behaviour Questionnaire (RBQ), and Responses to Uncertainty and Low Environment Structure (RULES), respectively. Parent-reported anxiety was determined using the Anxiety, Depression and Mood Scale (ADAMS). 

Results. Pearson correlations revealed that sensory sensitivities [p = 0.008], RRBs [p = 0.030], and IU [p < 0.001] were positively associated with anxiety in FXS. 

Conclusion. These results suggest that people with FXS that experience greater difficulties with sensory sensitivities, RRBs, and tolerating uncertainty are more likely to experience anxiety. Although additional work is needed, understanding the underlying factors that contribute to the relationship between autism characteristics, IU, and anxiety in rare genetic syndromes will serve to improve theoretical models and targeted interventions.

Keywords: Fragile X syndrome, anxiety, autism, intolerance of uncertainty