Age of First Words Predicts Cognitive Ability and Adaptive Skills in Children with ASD

Background:

Children with ASD generally achieve language milestones, particularly expressive language milestones, later than children with typical development. Early reports of ASD identified age of language acquisition as an important indicator of positive prognosis; specifically, language by age 5-6 years was described as an important discriminator of higher versus lower functioning in ASD. In recent years, children have been diagnosed with ASD at younger ages, which allows for an earlier investigation of the relationship between language acquisition and later development. 

Objectives:  

The current study examines the relationship between early language acquisition and later functioning in children with ASD by examining how the age of a child’s first word predicts later cognitive ability, adaptive behavior, and ASD severity.  

Methods:  

The sample consisted of 119 children with ASD who were ascertained by screening positive on the M-CHAT at age two.  The sample was primarily male (83.2%) and White (82.4%). Children ranged in age at the time of the evaluation from 45 - 72 months, with a mean age of 52.2 months (SD = 6.1).  Cognitive ability and adaptive skills were assessed using the Mullen Scales of Early Learning (MSEL) and the Vineland Adaptive Behavior Scales (VABS); parents recalled the age of their child’s first words during standard administration of the ADI-R.  

Results:  

Children were grouped based on the age by which they produced meaningful first words (i.e., 18, 24, 30, 36 months).  T-tests indicated that, for all significant results, children producing meaningful words by a given age performed significantly better on measures of cognition (MSEL) and adaptive skills (VABS) than the group of children who remained non-verbal at that benchmark. This difference was present as early as 18 months; as the age of comparison increased, more comparisons yielded significant results, and effect sizes became larger.  All comparisons were significant by 24 months, with medium effect sizes or larger, indicating that achieving first words by 24 months is a powerful prognostic indicator. Investigation of the age of first words using ANOVA and subsequent post hoc analyses indicated that first words by 24 months was associated with significantly better performance on MSEL language domains, VABS Communication and Social domains, and CARS total score when directly compared to children who achieved their first words by 30 months or later. The exceptions to these findings were ADOS severity score and DSM-IV total symptoms, which were similar in verbal versus non-verbal children at each comparison point.  

Conclusions:  

In summary, the current study of 119 children with ASD suggests that the age at which children speak their first words is strongly associated with better outcomes later in childhood. Children with first words by 24 months had higher cognitive ability and better adaptive skills than children who did not reach this milestone until later in life.  Identifying that acquisition of first words by 24 months is associated with a more positive prognosis will help parents and professionals prioritize treatment goals, and supports arguments against a “wait and see” approach to language delay, especially in the presence of any ASD symptoms.