Genetic variations that influence how active toddlers are may also be associated with a higher likelihood of attention deficit hyperactivity disorder (ADHD) later in life, according to a large international study. Researchers analysed data from nearly 80,000 infants from multiple British and European cohort studies. They found that about 10 per cent of the differences in toddlers’ activity levels could be explained by common genetic variants. Many of these genetic markers strongly overlapped with those already known to increase the chance of developing ADHD, a neurodevelopmental condition characterised by short attention spans and impulsive, restless behaviour.
“We did not know until now that the genetic basis of ADHD was shared with these early behavioural traits,” said first author Anja Hollowell of the Universities of Surrey and Birkbeck, UK, referring to the activity levels displayed in toddlers. She added, “Our findings show that very early activity levels are influenced by many of the same genetic markers that influence later ADHD. Earlier identification of ADHD would be very helpful for providing timely support to children and their families.”
The team identified genetic markers in the gene RHEBL1 that were associated with lower activity levels in toddlers and also appeared to increase the activity of the RHEBL1 gene in the brain’s cortex, a key region involved in cognition and behaviour. Lead author Angelica Ronald, Professor of Psychology and Genetics at the University of Surrey, said the period from 12 to 36 months is marked by rapid skill development and wide variation in how much young children move around, with activity levels shaping learning, exploration, motor skills and even the type of parenting they receive.
“For the first time, we have identified the genetic variation associated with these early behavioural traits in toddlers. Our work highlights the significance of ‘nature’ in a young child’s behaviour,” Ronald said. She noted that the study complements existing research on environmental influences in early childhood and advances understanding of how genetic and biological pathways contribute to individual differences in child development. The researchers say their findings open new avenues for exploring how early activity patterns are driven by biology and how they relate to brain development, learning and later mental health, including ADHD.
