Why Do Some Autistic Children Not Develop Speech, Even With Early Intervention?

This study analyzed data from over 700 autistic children who received early interventions focused on oral language development. Although most showed progress, about one-third remained with limited or absent speech. Early difficulties in cognition, social skills, and imitation were associated with the lack of progress. The results highlight the need for more individualized interventions.

Approximately one in three school-aged children diagnosed with autism spectrum disorder do not use spoken language as their primary form of communication. While language skills in autism vary widely and can change depending on the context, there is a specific group of children who reach school age with very limited or no speech.

This group is clinically important because the absence of oral language at this stage of life is associated with greater difficulties throughout development and adulthood.

Children who do not develop speech consistently during the preschool phase tend to face more academic, social, and adaptive challenges later in life. Therefore, since the first studies on autism intervention, the development of oral language has been considered one of the main therapeutic goals.

Over the last few decades, different types of early interventions have shown positive results for many children, especially when started early and carried out in a structured way.

Despite these advances, a significant portion of children do not show significant progress in oral language, even after receiving interventions considered effective. Existing studies show widely varying results on how many children remain non-verbal after early intervention, and there is still little clarity about who these children are and what characteristics are associated with the lack of progress.

Initial evidence suggests that difficulties in basic skills, such as cognition, social interaction, imitation, and pre-verbal communication, may be related to the persistence of minimal speech.

The lack of consistent information on the proportion and profile of these children represents a major obstacle to the personalization of interventions. Understanding why some children progress in oral language and others do not is essential for adjusting therapeutic strategies, setting realistic expectations, and improving long-term outcomes.

This study was developed precisely to fill these gaps. The researchers conducted a large-scale retrospective analysis to investigate how many autistic children did not acquire oral language, even after receiving evidence-based early interventions, and to identify common characteristics between those who progressed and those who did not progress in speech development.

To this end, a large dataset was used, gathering individual information from seven hundred and seven preschool children on the autism spectrum. The data analyzed in this study were obtained from early intervention programs conducted at university research centers. The children included in the study had received structured, evidence-based treatments in which the development of oral language was a central objective.

Oral language progress was carefully assessed using a combination of different sources of information. Parents reported how their children communicated in daily life, and this information was corroborated through direct assessments by professionals and by analyzing samples of the children's spontaneous language observed in natural contexts.

In addition to oral language, researchers also analyzed other skills present at the beginning of the intervention, such as cognition, social skills, adaptive behavior, and motor imitation ability. This information was used to identify which factors were associated with progress or lack of progress in spoken language.

Among the children who did not speak at the beginning of the study, about two-thirds began using at least isolated words or more complex forms of oral language after the intervention. However, approximately one-third remained non-verbal. These children showed, from the beginning, greater difficulties in imitating movements, an important skill for language learning.

Among the children who spoke very little at the beginning, approximately half managed to progress to word combinations by the end of the intervention. Children who did not reach this level presented, from the beginning, greater cognitive, social, adaptive, and imitative difficulties, in addition to having participated in interventions for shorter periods.

The age at which the intervention was initiated also had an impact, but differently depending on the child's initial language level. Interestingly, the specific type of intervention received did not seem to directly influence the likelihood of acquiring oral language, provided it was an evidence-based intervention.

These findings reinforce the importance of identifying at-risk profiles early and adapting interventions to the specific needs of each child, rather than adopting a one-size-fits-all approach.

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Proportion and Profile of Autistic Children Not Acquiring Spoken Language Despite Receiving Evidence-Based Early Interventions

Giacomo Vivanti,Michael V. Lombardo,Ashley Zitter,Brian Boyd,Cheryl Dissanayake,Sarah Dufek,Helen E. Flanagan,Suzannah Iadarola,Ann Kaiser,So Hyun Kim,Lynne Levato,Catherine Lord,Joshua Plavnick,Diana L. Robins,Sally J. Rogers,Isabel M. Smith,Tristram Smith,Aubyn Stahmer, and Linda Watson 

Journal of Clinical Child & Adolescent Psychology, 1-18. 

https://doi.org/10.1080/15374416.2025.2579286

Abstract:

To determine the proportion and profile of preschoolers on the autism spectrum who do not acquire spoken language despite receiving evidence-supported interventions that target spoken language. We examined an aggregate dataset comprising 707 preschoolers on the autism spectrum who had received evidence-supported interventions to determine the proportion and profile of those who experienced limited progress in spoken language. Interventions were delivered through programs affiliated with university research settings and ranged in duration from 6 to 24 months. Spoken language outcomes were determined from parent-report measures, which were validated against direct assessments and natural language samples. Approximately two-thirds of children who were non-speaking at baseline were using single words or more complex spoken language by intervention exit. Those who remained non-speaking had lower baseline motor imitation scores, derived mainly from parent reports. Approximately half of the children who were minimally speaking (i.e. had single words or no words) at baseline were combining words by intervention exit. Those who did not acquire word combinations had lower baseline scores in cognitive, social, adaptive and motor imitation measures, and shorter intervention duration. Age at intervention start influenced spoken language advancement differently depending on the initial spoken language level. The odds of acquiring spoken language did not differ based on the intervention received. Approximately one-third of children who had limited or no spoken language at baseline did not advance to spoken language stages following intervention. Development of spoken language was associated with modifiable factors at the child and intervention level.