In this comprehensive systematic review and meta-analysis of group design studies of nonpharmacological early interventions designed for young children with autism spectrum disorder (ASD), we report summary effects across 7 early intervention types (behavioral, developmental, naturalistic developmental behavioral intervention [NDBI], TEACCH, sensory-based, animal-assisted, and technology-based), and 15 outcome categories indexing core and related ASD symptoms. A total of 1,615 effect sizes were gathered from 130 independent participant samples. A total of 6,240 participants, who ranged in age from 0 -8 years, are represented across the studies. We synthesized effects within intervention and outcome type using a robust variance estimation approach to account for the nesting of effect sizes within studies. We also tracked study quality indicators, and report an additional set of summary effect sizes that restrict included studies to those meeting prespecified quality indicators. Finally, we conducted moderator analyses to evaluate whether summary effects across intervention types were larger for proximal as compared with distal effects, and for context-bound as compared to generalized effects. We found that when study quality indicators were not taken into account, significant positive effects were found for behavioral, developmental, and NDBI intervention types. When effect size estimation was limited to studies with randomized controlled trial (RCT) designs, evidence of positive summary effects existed only for developmental and NDBI intervention types. This was also the case when outcomes measured by parent report were excluded. Finally, when effect estimation was limited to RCT designs and to outcomes for which there was no risk of detection bias, no intervention types showed significant effects on any outcome.

We examined the quality of evidence supporting the effects of Naturalistic Developmental Behavioral Interventions (NBDIs) for facilitating change in young children with autism. We also investigated whether effects varied as a function of specific features of the intervention, samples, and outcomes measured. Twenty‐seven studies testing the effects of NDBIs were extracted from data collected for the Autism Intervention Meta‐analysis (Project AIM), a comprehensive meta‐analysis of group design, nonpharmacological intervention studies for children with autism aged 0–8 years. We extracted effect sizes for 454 outcomes from these studies for use in meta‐regression analyses testing associations between intervention effects and mean participant chronological age, language age, autism symptomatology, percentage of sample reported as male, cumulative intervention intensity, interventionist, outcome boundedness, outcome proximity, and risk of parent/teacher training correlated measurement error. The extant literature on NDBIs documents effects on social communication, language, play, and cognitive outcomes. However, our confidence in the positive and significant summary effects for these domains is somewhat limited by methodological concerns. Intervention effects were larger for context‐bound outcomes (relative to generalized), and for proximal outcomes (relative to distal). Our results indicate that NDBIs have promise as an approach for supporting development for some, but not all of the core and related features of autism in early childhood. Confidence in summary effect estimates is limited by study quality concerns, particularly an overreliance on measures subject to high detection bias. The results of this review support the use of proximity and boundedness as indicators of the limits of intervention effects. Lay summary Naturalistic Developmental Behavioral Interventions may increase language, social communication, play skills, and cognition in young children with autism, but these increases are largest for skills directly targeted by the intervention, and in contexts that are similar to that of the intervention. These conclusions are tempered by some concerns regarding research design across the studies that have been conducted to date. Autism Res 2021, 14: 817–834. © 2021 International Society for Autism Research and Wiley Periodicals LLC

Purpose This study synthesized effects of interventions on language outcomes of young children (ages 0–8 years) with autism and evaluated the extent to which summary effects varied by intervention, participant, and outcome characteristics. Method A subset of effect sizes gathered for a larger meta-analysis (the Autism Intervention Meta-analysis or Project AIM) examining the effects of interventions for young children with autism, which were specific to language outcomes, was analyzed. Robust variance estimation and metaregression were used to calculate summary and moderated effects while controlling for intercorrelation among outcomes within studies. Results A total of 221 outcomes were gathered from 60 studies. The summary effect of intervention on language outcomes was small but significant. Summary effects were larger for expressive and composite language outcomes compared to receptive language outcomes. Interventions implemented by clinicians, or by clinicians and caregivers together, had summary effects that were significantly larger than interventions implemented by caregivers alone. Participants' pretreatment language age equivalent scores positively and significantly moderated intervention effects, such that effects were significantly larger on average when samples of children had higher pretreatment language levels. Effects were not moderated by cumulative intervention intensity, intervention type, autism symptomatology, chronological age, or the proximity or boundedness of outcomes. Study quality concerns were apparent for a majority of included outcomes. Conclusions We found evidence that intervention can facilitate improvements in language outcomes for young children with autism. Effects were largest for expressive and composite language outcomes, for children with initially higher language abilities, and for interventions implemented by clinicians or by caregivers and clinicians combined. However, quality concerns of included studies and borderline significance of some results temper our conclusions regarding intervention effectiveness and corresponding moderators.

Our team examined 150 reports on group-design, non-pharmacological interventions for young autistic children, to determine the prevalence of adverse event reporting. We found that only 11 studies mentioned adverse events; one indicated adverse events occurred, and an additional three indicated adverse effects occurred (i.e. adverse events that could be attributed to the intervention). We also coded reasons for participant withdrawal and found that of the 54 studies that reported reasons for withdrawal, 10 studies reported reasons that could be categorized as adverse events, 8 reported reasons that could be categorized as adverse effects, and an additional 12 studies reported reasons that were too vaguely described to determine adverse event status. We recommend that autism intervention researchers make concerted efforts to monitor, classify, and report adverse events so that practitioners, policy-makers, and families are better equipped to weigh potential benefits of interventions against potential harms. Lay abstract In this study, we looked at published research on interventions for young autistic children that did not involve administering medication. We were interested in determining how often studies reported on whether adverse events (i.e. physical or psychological distress to the participants) or adverse effects (i.e. adverse events that are thought to be caused by the intervention) had occurred. We found that of the 150 reports we examined, only 11 mentioned adverse events. One of these studies reported adverse events occurred, and three reported that adverse effects occurred. We also reviewed the studies to examine the reasons that were given to explain why any participants dropped out of the intervention (termed “withdrawal”), to determine if any of these reasons could be considered adverse events or adverse effects. Fifty-four studies described reasons for withdrawal, and 10 of these studies had reasons that could be categorized as an adverse event, 8 studies had reasons that could be categorized as an adverse effect, and an additional 12 studies had reasons that were too vaguely described to determine whether they were adverse events or not. We recommend that autism intervention researchers develop more systematic methods of looking for and reporting adverse events and effects, so that professionals and families can be better informed when choosing to enroll their autistic children in interventions.

Background: The presence, types, disclosure rates, and effects of conflicts of interest (COIs) on autism early intervention research have not previously been studied. The purpose of this study was to examine these issues. Methods: This study is a secondary analysis of a comprehensive meta-analysis of all group-design, nonpharmacological early intervention autism research conducted between 1970 and 2018. We coded reports for the presence/ absence of COI statements, the types of COIs that were disclosed, and for 8 types of COIs, including (a) the author developed the intervention, (b) the author is affiliated with a clinical provider, (c) the author is employed by a clinical provider, (d) the author is affiliated with an institution that trains others to use the intervention, (e) the author receives payment or royalties related to the intervention, (f) the study was funded by an intervention provider, (g) the study used a commercially available measure developed by the author, and (h) proceeds of the intervention fund the author's research. Frequencies and proportions were calculated to determine prevalence of COIs and COI disclosures. Meta-analysis was used to estimate summary effects by COI type and to determine if they were larger than for reports with no coded COIs. Results: Seventy percent of reports were coded for ≥ 1 COI, but only~6% of reports contained COI statements fully accounting for all coded COIs. Metaregressions did not detect significant influences of any COI type on summary effects; however, point estimates for each COI type were larger than for reports with no coded COIs. Conclusions: Conflicts of interest are prevalent but under-reported in autism early intervention research. Improved reporting practices are necessary for researcher transparency and would enable more robust examination of the effects of COIs on research outcomes.