In a groundbreaking study set to reshape our understanding of early childhood development, researchers from the University of Surrey have identified specific genetic variations that influence toddler activity levels. This unprecedented research, led by Professor Angelica Ronald, illuminates how these genetic markers are not only pivotal in shaping a child’s activity in their earliest years but also share significant overlap with genes associated with Attention Deficit Hyperactivity Disorder (ADHD), a diagnosis that typically emerges later in childhood or even adulthood.
Activity levels in toddlers have long been observed to vary widely among individuals, influenced by a mixture of environmental and biological factors. However, this study is the first large-scale investigation to pinpoint the genetic architecture underpinning these early behavioral traits. By analyzing genetic data from nearly 80,000 infants across multiple international cohort studies, the team undertook a comprehensive genome-wide association study (GWAS) that allowed them to map out the specific DNA sequences correlated with differences in toddler activity.
The developmental window from 12 to 36 months marks a critical period where fundamental motor and cognitive skills emerge. Professor Ronald explains that toddlers differ dramatically in their propensity to move, ranging from those who prefer calm, stationary behaviors to those exhibiting heightened levels of physical activity. These early activity patterns are crucial as they can influence how children explore their environments, acquire motor proficiencies, and even elicit varying types of parental responses.
Delving into the biology behind these behaviors, the researchers discovered that approximately 10 percent of the variance in toddler activity levels could be attributed to common genetic differences. One particularly intriguing finding centers on genetic variations in the RHEBL1 gene. These specific markers were linked to lower activity levels in toddlers and were found to affect the gene’s expression within the cortex — a significant brain region involved in higher-order cognitive functions and motor control.
The increase in RHEBL1 activity in the cortex connected with these genetic variants offers a compelling biological explanation for how differences in DNA can translate into observable behavior during infancy. This linkage between gene expression in neural tissue and early movement patterns has profound implications, potentially paving the way for understanding how early brain development factors into later cognitive and behavioral outcomes.
Leader of the first author team, Anja Hollowell, now at University College London, highlights that these insights reaffirm the shared genetic etiology between toddler activity and ADHD, a disorder characterized by inattention, hyperactivity, and impulsivity. The recognition that the genetic foundation of ADHD overlaps with early-life activity behaviors opens promising avenues for earlier diagnosis and intervention strategies, potentially supporting affected children and their families much sooner.
Beyond activity levels, the study extended its scope to other core dimensions of temperament such as sociability, emotionality, and shyness. The researchers identified multiple genetic markers intricately involved in these traits as well, elucidating the biological underpinnings behind wide behavioral variations from infancy. For example, genetic variants tied to heightened emotionality in toddlers were also connected with neurotic personality traits in adults, suggesting a developmental continuity of temperament rooted in genetics.
Moreover, the genetic variations correlating with low sociability and elevated emotionality displayed significant overlap with markers associated with autism spectrum disorder (ASD). These findings suggest a complex genetic network influencing diverse aspects of early temperament and potentially serving as early indicators for neurodevelopmental conditions, emphasizing the critical role of nature alongside nurture.
This pioneering research underscores the importance of genetic contributions during early childhood behaviors, complementing the wealth of existing studies focused on environmental influences. Understanding the magnitude and mechanisms of these genetic effects contributes to a more holistic view of child development, highlighting intricate interactions between inherited biology and external factors from the earliest stages of life.
The implications of this work stretch beyond academic curiosity. By mapping genetic variations linked to early temperament traits, scientists can better appreciate how biology shapes developmental trajectories and identify children who may benefit from tailored early interventions. This is especially relevant for conditions such as ADHD and autism, where early support can profoundly improve long-term outcomes.
Published in Nature Human Behaviour, this research stands at the forefront of behavioral genetics, seeking to unravel the genomic tapestries that govern human behavior from infancy onward. The study not only enriches our grasp of toddler activity and temperament but also bridges gaps between early life biology, brain development, and the emergence of complex neuropsychiatric conditions.
In sum, this international collaboration has set a new benchmark in the field of developmental psychology and genetics, revealing that the roots of certain behaviors and conditions lie deep within our DNA. These insights hold the promise of revolutionizing early childhood assessments, interventions, and ultimately, the lifelong wellbeing of individuals shaped by the interplay of their genetic blueprint and environment.
Subject of Research: Genetic influences on toddler activity levels and their association with ADHD and other temperament traits
Article Title: ‘Genome-wide association studies of infant temperament reveal genetic links with later life outcomes’
News Publication Date: 1 July 2026
Web References:
https://www.nature.com/articles/s41562-026-02486-5
References:
Ronald, A. et al. Genome-wide association studies of infant temperament reveal genetic links with later life outcomes. Nature Human Behaviour, DOI: 10.1038/s41562-026-02486-5 (2026).
Keywords: toddler activity levels, genetics, ADHD, infant temperament, genome-wide association study, RHEBL1 gene, neurodevelopment, early intervention, autism spectrum disorder, emotionality, sociability, behavioral genetics
