Objective To summarize the breadth and quality of evidence supporting commonly recommended early childhood autism interventions and their estimated effects on developmental outcomes. Design Updated systematic review and meta-analysis (autism intervention meta-analysis; Project AIM). Data sources A search was conducted in November 2021 (updating a search done in November 2017) of the following databases and registers: Academic Search Complete, CINAHL Plus with full text, Education Source, Educational Administration Abstracts, ERIC, Medline, ProQuest Dissertations and Theses, PsycINFO, Psycholog...