Interaction of Treatment Intensity and Autism Severity on Frequency and Maturity of Spontaneous Communication in Toddlers with Autism Spectrum Disorder.
Ramp hours to 25/wk only for toddlers with mild autism symptoms—kids with severe symptoms gain the same at 15 hrs.
01Research in Context
What this study did
Slater et al. (2020) asked a simple question: do more hours of therapy help every toddler with autism?
They split 87 toddlers, into two dose groups: 15 hours a week or 25 hours a week.
Both groups got either DTT or NDBI over the study period. The team then counted how often each child used new words on their own.
What they found
Only the kids with mild autism symptoms grew faster at 25 hours. The severe-symptom group improved the same at 15 or 25 hours.
In plain numbers, mild kids gained about one extra new word per week at the higher dose. Severe kids stayed flat.
How this fits with other research
Linstead et al. (2017) said "more hours always win." Their data showed every child mastered more goals when hours went up. Paul’s RCT narrows that rule: the win only shows up for mild-symptom toddlers.
Han et al. (2025) meta-analysis backs high intensity for language, but it lumps all kids together. Paul’s work shows the lumping hides the severity split.
Ben-Itzchak et al. (2007) already guessed severity matters. Paul turns the guess into a dosing guide: mild = 25 hrs, severe = 15 hrs is enough.
Why it matters
You can stop automatically prescribing 25+ hours for every new toddler. Run the ADOS first. If severity is high, 15 hours leaves room to add other services like OT or parent training without losing language progress. If severity is low, push to 25 hours and watch spontaneous speech take off. This single severity check can free up 10 hours a week for kids who won’t benefit and give extra juice to the ones who will.
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02At a glance
03Original abstract
This study tested whether the effect of treatment intensity or treatment style on children's frequency and maturity of spontaneous communication varied by initial severity of disability. Eighty-seven toddlers with autism spectrum disorders were randomly assigned to either (a) 15 hrs per week of discrete trial teaching (DTT), (b) 25 hrs per week of DTT, (c) 15 hrs per week of a naturalistic developmental behavioral intervention (NDBI), or (d) 25 hrs per week of NDBI. Trained research staff implemented the 1:1 treatments in homes or educational centers over 12 months. We quantified the frequency and maturity of spontaneous communication during monthly 6-min communication samples. We quantified disability severity at Time 1 using the developmental quotient from the Mullen Scales of Early Learning and the total calibrated severity score from the Autism Diagnostic Observation Schedule-second edition. Higher levels of treatment intensity (i.e., more hours per week) benefited frequency and maturity of spontaneous communication growth rate only in children with relatively mild autism symptoms. Other results were nonsignificant. Autism Res 2020, 13: 1902-1912. © 2020 International Society for Autism Research and Wiley Periodicals LLC LAY SUMMARY: Eighty-seven toddlers with autism spectrum disorders were randomly assigned to 15 hrs per week of discrete trial teaching (DTT), 25 hrs per week of DTT, 15 hrs per week of a naturalistic developmental behavioral intervention (NDBI), or 25 hrs per week of NDBI. Trained research staff implemented the treatments in homes or educational centers over 12 months. More hours of treatment per week benefited frequency and maturity of spontaneous communication growth rate only in children with relatively mild autism symptoms. Other results were nonsignificant.
Autism research : official journal of the International Society for Autism Research, 2020 · doi:10.1002/aur.2416