Infancy & early childhood motor activity levels as predictors of attention-deficit/hyperactivity disorder: a systematic review of cross-sectional and longitudinal studies

Attention-Deficit/Hyperactivity Disorder (ADHD) is a heterogeneous neurodevelopmental condition characterised by inattention, impulsivity, and hyperactivity. Although motor overactivity is a defining feature of the ADHD phenotype, its role in early development remains unclear. This PRISMA 2020 systematic review synthesised evidence on associations between early motor activity levels and later ADHD traits or diagnosis, and appraised both methodological quality and conceptual framing within the literature. Searches identified 1,469 records, of which 19 studies met inclusion criteria. Studies assessed motor activity using objective measures (e.g., actigraphy/accelerometry), parent or multi-informant reports, or combined multi-method designs. Across methodologies, heightened or poorly regulated early activity was consistently associated with later ADHD traits and/or diagnosis, with signals detectable from infancy and toddlerhood. Evidence also suggested heterogeneity in early motor profiles: while many studies linked elevated activity to ADHD outcomes, a subset reported associations between motor delays or broader motor atypicalities and later ADHD traits. Multi-informant and multi-modal approaches generally provided the most robust developmental signal. Beyond empirical synthesis, the review identified a predominance of deficit-oriented language and diagnosis-focused endpoints, alongside emerging dimensional and neurodiversity-informed alternatives. Overall, early motor behaviour appears to be a multifaceted, developmentally salient indicator of ADHD propensity. Future research should integrate objective, informant, and genetic data within dimensional frameworks to clarify when, for whom, and through which mechanisms early motor activity relates to the unfolding of attentional, emotional, and cognitive development.