Minimally verbal status in children with intellectual disability of genetic origin – prevalence, functional impact and relationship with motor skills: evidence from the IMAGINE-ID cohort

Abstract Background Up to a third of autistic children do not develop functional speech and remain minimally verbal (MV) beyond the age of 5, yet little is known about the clinical characteristics of this group. Less still is known about the prevalence or impact of MV status in children with intellectual disability. Our objective was to provide further insights into the clinical phenotype of MV children with ID. To do so, we investigated the prevalence of MV status in children with intellectual disability (ID) and genetic conditions, with and without a co-occurring autism diagnosis. We also investigated the association between communication ability (MV status) and outcomes known to be associated with MV status, including adaptive function, motor abilities and emotional and behavioural difficulties. Methods A pre-registered secondary data analysis using cross-sectional parent-reported data from children with ID of genetic origin (IMAGINE-ID https://imagine-id.org/ ): We (1) compared the prevalence of MV status in children with ID with and without co-occurring autism and (2) quantified associations between MV status and adaptive function, motor abilities and emotional and behavioural difficulties while controlling for autism diagnoses. Results One in five children with ID of genetic aetiology were ascertained to be MV. Of those who were MV, 31% met criteria for an autism diagnosis and 69% did not. In our ID cohort, being MV was associated with lower adaptive scores, yet (contrary to expectation) fewer emotional and behavioural difficulties. Significantly more MV participants had gross motor difficulties, but the groups did not differ on fine motor skills. In a subsample of participants where more fine-grained data were available ( n = 210), our models showed that MV status is significantly associated with adaptive function, fine and gross motor skills, and emotional and behavioural difficulties, even when controlling for autism diagnosis, sex, age and socioeconomic status. Conclusions Taken as a whole, these findings suggest a need for greater awareness in research and practice of MV individuals who may not be autistic. Regardless of autism status, being MV associates with low adaptive outcomes. Further research is needed to explore the contradictory finding that MV children exhibit lower behavioural and emotional problems. Motor skill challenges associated with MV status, suggesting we should develop supports and interventions for MV children that take motor planning difficulties into account.