A randomised-controlled trial of a pre-emptive intervention for infants showing early behavioural risk signs of autism spectrum disorder

‘High functioning autism’ is a term often used for individuals with autism spectrum disorder without an intellectual disability. Over time, this term has become synonymous with expectations of greater functional skills and better long-term outcomes, despite contradictory clinical observations. This study investigated the relationship between adaptive behaviour, cognitive estimates (intelligence quotient) and age at diagnosis in autism spectrum disorder. Participants ( n = 2225, 1–18 years of age) were notified at diagnosis to a prospective register and grouped by presence ( n = 1041) or absence ( n = 1184) of intellectual disability. Functional abilities were reported using the Vineland Adaptive Behaviour Scales. Regression models suggested that intelligence quotient was a weak predictor of Vineland Adaptive Behaviour Scales after controlling for sex. Whereas the intellectual disability group’s adaptive behaviour estimates were close to reported intelligence quotients, Vineland Adaptive Behaviour Scales scores fell significantly below intelligence quotients for children without intellectual disability. The gap between intelligence quotient and Vineland Adaptive Behaviour Scales scores remained large with increasing age at diagnosis for all children. These data indicate that estimates from intelligence quotient alone are an imprecise proxy for functional abilities when diagnosing autism spectrum disorder, particularly for those without intellectual disability. We argue that ‘high functioning autism’ is an inaccurate clinical descriptor when based solely on intelligence quotient demarcations and this term should be abandoned in research and clinical practice.

Key Points Question Does preemptive intervention compared with usual care reduce the severity of autism symptoms and the likelihood of an autism spectrum disorder (ASD) diagnosis in infants showing early signs of ASD? Findings In this randomized clinical trial of 103 infants showing early behavioral signs of ASD, preemptive intervention led to a statistically significant reduction in the severity of ASD behaviors across early childhood. Infants who received the preemptive intervention had lower odds of meeting diagnostic criteria for ASD (7%) than those who received usual care (21%) at age 3 years, with a number needed to treat of 7 participants. Meaning This study found that a preemptive intervention reduced ASD diagnostic behaviors when used at the time atypical development first emerges during infancy.