Moderators of response to stimulants for preschool attention-deficit/hyperactivity disorder

Abstract

Objective: this study aimed at identifying moderators of efficacy of stimulants against placebo to inform personalized recommendations for treatment in preschool children (< 6 years) with attention-deficit/hyperactivity disorder (ADHD).

Method: we acquired individual-level participant data from two randomized placebo-controlled trials (RCTs) of preschool ADHD: MAPPA (8-week methylphenidate, 102 participants, Brazil) and SPD489-347 (6-week lisdexamfetamine, 148 participants, US). We evaluated the moderator and predictor effects of baseline demographic (age, sex, race, ethnicity, maternal educational level) and baseline clinical (ADHD symptom severity, intelligence quotient, number of psychiatric comorbidities) characteristics, as available, on endpoint ADHD symptom severity scores. Data from each study were analyzed separately with linear mixed-effects model for repeated measures. For categorical variables, we also computed treatment effects (i.e., stimulants versus placebo) within subgroups and, when possible, pooled them alongside subgroup data from PATS (5-week methylphenidate, 165 participants, US) in random-effects meta-analyses.

Results: stimulants had greater efficacy against placebo in White children compared to Black children considering data from US studies. Older age was not a moderator of greater efficacy of stimulants against placebo, nor was it associated with worse ADHD symptom severity at endpoint. Greater baseline ADHD symptom severity was associated with higher ADHD symptom severity at endpoint independently of the assigned treatment group.

Conclusion: race, but not older age or baseline ADHD symptom severity, may moderate the efficacy of stimulants for preschool ADHD. Given the post hoc nature of subgroup analyses, the findings should be interpreted as exploratory and viewed as hypothesis for confirmation in future studies.

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Identifiers

ORCID for Samuele Cortese: orcid.org/0000-0001-5877-8075

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