Intellectual functioning and adaptive behaviour in children with Dravet syndrome: A population-based study.

AIM: To identify, on a population basis, the prevalence of intellectual disability in children with Dravet syndrome, profiles on a measure of adaptive behaviour, and factors associated with intellectual functioning and adaptive behaviour. METHOD: Forty-two out of 48 children with Dravet syndrome living in Sweden, born between 1st January 2000 and 31st December 2018, underwent assessment of intellectual functioning and adaptive behaviour. Factors associated with level of intellectual functioning and adaptive behaviour were analysed. RESULTS: Eight-six per cent (n = 36) of the children fulfilled DSM-5 criteria for intellectual disability (29% [n = 12] mild intellectual disability, 24% [n = 10] moderate intellectual disability, 33% [n = 14] severe intellectual disability, 0% profound intellectual disability) and 93% (n = 39) had an adaptive behaviour composite more than two standard deviations below the mean. Communication was a significant weakness compared with daily living skills (p < 0.001; mean difference 95% confidence interval [CI] -8.193 to -4.092) and socialization (p = 0.001; mean difference 95% CI 6.511 to -1.775) on the Vineland Adaptive Behavior Scales, Second Edition. The only factors significantly associated with both decreased adaptive behaviour and presence of severe intellectual disability was the presence of increased autistic symptoms and younger age. INTERPRETATION: Children with Dravet syndrome have a very high level of intellectual disability and almost all have significant deficits in adaptive behaviour. Greater deficits in adaptive behaviour and greater severity of intellectual disability are associated with the presence of increased autistic symptoms, highlighting the need for comprehensive neurodevelopmental assessment for all affected children. WHAT THIS PAPER ADDS: Eighty-six per cent (n = 36) of children with Dravet syndrome fulfilled criteria for intellectual disability. Ninety-three per cent (n = 39) of children with Dravet syndrome had significant deficits in adaptive behaviour. Communication was a significant weakness on a measure of adaptive behaviour. Increased autistic symptoms were associated with greater deficits in cognition/adaptive behaviour. Older age and earlier status epilepticus were associated with decreased adaptive behaviour.