Determining Associations Between Intervention Amount and Outcomes for Young Autistic Children: A Meta-Analysis.

Importance: Health professionals routinely recommend intensive interventions (ie, 20-40 hours per week) for autistic children. However, primary research backing this recommendation is sparse and plagued by methodological flaws.
Objective: To examine whether different metrics of intervention amount are associated with intervention effects on any developmental domain for young autistic children.
Data Sources: A large corpus of studies taken from a recent meta-analysis (with a search date of November 2021) of early interventions for autistic children.
Study Selection: Studies were eligible if they reported a quasi-experimental or randomized clinical trial testing the effects of a nonpharmacological intervention on any outcome in participant samples comprising more than 50% autistic children 8 years or younger.
Data Extraction and Synthesis: Data were independently extracted by multiple coders. Meta-regression models were constructed to determine whether each index of intervention amount was associated with effect sizes for each intervention type, while controlling for outcome domain, outcome proximity, age of participants, study design, and risk of detection bias. Data were analyzed from June 2023 to February 2024. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.
Main Outcomes and Measures: The primary predictor of interest was intervention amount, quantified using 3 different metrics (daily intensity, duration, and cumulative intensity). The primary outcomes of interest were gains in any developmental domain, quantified by Hedges g effect sizes.
Results: A total of 144 studies including 9038 children (mean [SD] age, 49.3 [17.2] months; mean [SD] percent males, 82.6% [12.7%]) were included in this analysis. None of the meta-regression models evidenced a significant, positive association between any index of intervention amount and intervention effect size when considered within intervention type.
Conclusions and Relevance: Findings of this meta-analysis do not support the assertion that intervention effects increase with increasing amounts of intervention. Health professionals recommending interventions should be advised that there is little robust evidence supporting the provision of intensive intervention.