Social and emotional characteristics of girls and young women withDDX3X-linked intellectual disability: A descriptive and comparative study

Background DDX3X variants are a common cause of intellectual disability (ID) in females. Previous studies have reported high rates of autism spectrum disorder and emotional-behavioural difficulties within this group. However, no study has compared social and emotional characteristics in individuals with DDX3X variants to individuals with other monogenic causes of ID. Methods Twenty-three females with pathogenic or likely pathogenic DDX3X variants were recruited via UK regional genetics centres, genetic research cohorts, and family support groups. Twenty-three females with ID and variants in other genes were recruited via the same routes. Phenotypic data were collected through semi-structured interviews and standardised questionnaires. Results In line with previous research, we found a wide range of adaptive, social and emotional function within the DDX3X group. Autism characteristics assessed via the Social Responsiveness Scale (SRS) did not differ between DDX3X and comparison groups, while levels of anxiety and self-injurious behaviour (SIB) scores assessed via the Developmental Behaviour Checklist (DBC) were significantly higher in the DDX3X group. Autistic characteristics, anxiety and SIB scores were positively correlated within the DDX3X group. Individuals with DDX3X missense variants had poorer adaptive abilities than those with protein truncating variants as previously reported, but DDX3X variant type did not significantly predict emotional and behavioural characteristics. Conclusions We provide quantitative evidence that overall incidence of autistic characteristics is not higher amongst girls and women with DDX3X variants than expected for ID. However, the DDX3X group demonstrates more SIBs and anxiety symptoms than expected, with close relationships between SIBs and anxiety, and between anxiety and autistic characteristics. Future work is warranted to explore the multilevel mechanisms contributing to social and emotional development in individuals with DDX3X variants, and consider whether these mechanisms are specific to this genetic diagnosis or shared with a subset of people with ID due to other causes.