The rising prevalence of autism spectrum disorders (ASD) increases the need for evidence‐based behavioral treatments to lessen the impact of symptoms on children's functioning. At present, there are no curative or psychopharmacological therapies to effectively treat all symptoms of the disorders. Early intensive behavioral intervention (EIBI) is a treatment based on the principles of applied behavior analysis. Delivered for multiple years at an intensity of 20 to 40 hours per week, it is one of the more well‐established treatments for ASD. This is an update of a Cochrane review last published in 2012. To systematically review the evidence for the effectiveness of EIBI in increasing functional behaviors and skills, decreasing autism severity, and improving intelligence and communication skills for young children with ASD. We searched CENTRAL, MEDLINE, Embase, 12 additional electronic databases and two trials registers in August 2017. We also checked references and contacted study authors to identify additional studies. Randomized control trials (RCTs), quasi‐RCTs, and controlled clinical trials (CCTs) in which EIBI was compared to a no‐treatment or treatment‐as‐usual control condition. Participants must have been less than six years of age at treatment onset and assigned to their study condition prior to commencing treatment. We used standard methodological procedures expected by Cochrane. We synthesized the results of the five studies using a random‐effects model of meta‐analysis, with a mean difference (MD) effect size for outcomes assessed on identical scales, and a standardized mean difference (SMD) effect size (Hedges' g) with small sample correction for outcomes measured on different scales. We rated the quality of the evidence using the GRADE approach. We included five studies (one RCT and four CCTs) with a total of 219 children: 116 children in the EIBI groups and 103 children in the generic, special education services groups. The age of the children ranged between 30.2 months and 42.5 months. Three of the five studies were conducted in the USA and two in the UK, with a treatment duration of 24 months to 36 months. All studies used a treatment‐as‐usual comparison group. Primary outcomes We found evidence at post‐treatment that EIBI improves adaptive behaviour (MD 9.58 (assessed using Vineland Adaptive Behavior Scale (VABS) Composite; normative mean = 100, normative SD = 15), 95% confidence interval (CI) 5.57 to 13.60, P < 0.001; 5 studies, 202 participants; low‐quality evidence; lower values indicate positive effects). We found no evidence at post‐treatment that EIBI improves autism symptom severity (SMD −0.34, 95% CI −0.79 to 0.11, P = 0.14; 2 studies, 81 participants; very low‐quality evidence). No adverse effects were reported across studies. Secondary outcomes We found evidence at post‐treatment that EIBI improves IQ (MD 15.44 (assessed using standardized IQ tests; scale 0 to 100, normative SD = 15), 95% CI 9.29 to 21.59, P < 0.001; 5 studies, 202 participants; low‐quality evidence) and expressive (SMD 0.51, 95% CI 0.12 to 0.90, P = 0.01; 4 studies, 165 participants; low‐quality evidence) and receptive (SMD 0.55, 95% CI 0.23 to 0.87, P = 0.001; 4 studies, 164 participants; low‐quality evidence) language skills. We found no evidence at post‐treatment that EIBI improves problem behaviour (SMD −0.58, 95% CI −1.24 to 0.07, P = 0.08; 2 studies, 67 participants; very low‐quality evidence). There is weak evidence that EIBI may be an effective behavioral treatment for some children with ASD; the strength of the evidence in this review is limited because it mostly comes from small studies that are not of the optimum design. Due to the inclusion of non‐randomized studies, there is a high risk of bias and we rated the overall quality of evidence as 'low' or 'very low' using the GRADE system, meaning further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. It is important that providers of EIBI are aware of the current evidence and use clinical decision‐making guidelines, such as seeking the family’s input and drawing upon prior clinical experience, when making recommendations to clients on the use EIBI. Additional studies using rigorous research designs are needed to make stronger conclusions about the effects of EIBI for children with ASD. Early intensive behavioral intervention (EIBI) for increasing functional behaviors and skills in young children with autism spectrum disorders (ASD) What is the aim of this review? The aim of this review was to find out whether early intensive behavioral intervention (EIBI) can improve functional behaviors and skills, reduce the severity of autism, and improve intelligence and communication skills for young children (less than six years old) with autism spectrum disorders, also called ASD. Cochrane researchers gathered and analysed all relevant studies to answer this question and found five relevant studies. Key messages The evidence supports the use of EIBI for some children with ASD. However, the results should be interpreted with caution, as the quality of the evidence is weak; only a small number of children were involved in the studies, and only one study had an optimum design in which children were randomly assigned to treatment groups. What was studied in the review? We examined EIBI, which is a commonly used treatment for young children with ASD. We looked at the effect of EIBI on adaptive behavior (behaviors that increase independence and the ability to adapt to one's environment); autism symptom severity; intelligence; social skills; and communication and language skills. What are the main results of this review? We found five relevant studies, which lasted between 24 months and 36 months. Of the five studies, three were conducted in the USA and two in the UK. Only one study randomly assigned children to a treatment or comparison group, which is considered the 'gold standard' for research. The other four studies used parent preference to assign children to groups. A total of 219 children were included in the five studies; 116 children in the EIBI groups and 103 children in generic, special education services groups. All children were younger than six years of age when they started treatment; their ages ranged between 30.2 months and 42.5 months. These studies compared EIBI to generic, special education services for children with ASD in schools. Review authors examined and compared the results of all five studies. They found weak evidence that children receiving the EIBI treatment performed better than children in the comparison groups after about two years of treatment on scales of adaptive behavior, intelligence tests, expressive language (spoken language), and receptive language (the ability to understand what is said). Differences were not found for the severity of autism symptoms or a child's problem behavior. No study reported adverse events (deterioration in adaptive behaviour or autism symptom severity) due to treatment. How up‐to‐date is this review? The review authors searched for studies that had been published up to August 2017.
