Efficacy of stimulants for preschool attention-deficit/hyperactivity disorder: A systematic review and meta-analysis

Background: Robust synthesis of evidence to support treatment recommendations for preschoolers with attention-deficit/hyperactivity disorder (ADHD) is lacking. The aim of this systematic review and meta-analysis was to review currently available evidence to evaluate the efficacy and acceptability of stimulants for preschool children with ADHD. Methods: We searched electronic databases (CENTRAL, Embase, PubMed) from the database inception to March, 2022; and clinical trial registries through WHO ICTRP from the database inception to July, 2022, and selected double-blinded randomized controlled trials (RCTs) that compared stimulants against placebo for the treatment of preschoolers (age <= 7 years) with ADHD. Change in ADHD symptom severity was the primary outcome (efficacy) and all-cause dropout rates (acceptability) was the secondary outcome. Data were pooled with random-effects models weighted by the inverse of the variance. Risk of bias of individual studies were assessed with the Cochrane Risk of Bias tool version 2. The Grading of Recommendations Assessment, Development, and Evaluation approach was used to assess the quality of evidence. This study is registered with PROSPERO (CRD42022348597). Results: Five RCTs (three methylphenidate immediate-release, one methylphenidate extended-release, and one lisdexamfetamine) were included. The analysis of efficacy was based on 489 participants. Meta-analysis of change in ADHD symptom severity demonstrated a significant effect in favor of stimulants over placebo (standardized mean difference = -0.59; 95% CI -0.77, -0.41; p < 0.0001). There was no evidence of heterogeneity but some concerns about publication bias. Regardless, the confidence of evidence was considered moderate. For acceptability, stimulants did not lead to an increased rate of all-cause discontinuation rates in comparison to placebo (OR = 0.59; 95% CI 0.15, 2.37; p = 0.45) but the confidence of estimate was very low. Conclusions: Our findings demonstrated that stimulants are efficacious in reducing ADHD symptoms among preschool children. Clinicians should consider the use of stimulants when making treatment recommendations for preschoolers with ADHD.