Babies who start walking later ‘less likely to have ADHD’

The age at which babies take their first steps is strongly influenced by their genes – and could even have a bearing on school success and the likelihood of developing ADHD, researchers have discovered.

Babies who start walking later than average have less chance of developing attention deficit hyperactivity disorder (ADHD), scientists from the University of Surrey and University of Essex found.

They analysed the genetic information of more than 70,000 infants of European ancestry and identified 11 genetic markers influencing when babies start walking.

Researchers believe their findings could improve public health policies by helping to identify children who need clinical help at an earlier stage.

The study found that the genetic factors influencing when children take their first steps – a moment embedded on every parent’s brain and which typically occurs between 8 and 18 months – are partly the same as the genetic factors that influence brain development including the amount of folding and ridges in the outer surface of the brain, the cortex.

In a finding the scientists said may surprise parents as delayed walking is associated with increased likelihood of developmental disorders, the latest study found walking later was linked genetically with less chance of developing ADHD.

Around 708,000 children in the UK have ADHD, according to ADHD UK, but some medics claim it is overdiagnosed in both children and adults.

In early childhood the onset of walking is used as a simple yet robust clinical marker for brain and behavioural development, the researchers said. Current clinical guidelines state that babies who cannot walk independently by the time they are 18 months should be referred to a paediatrician for further assessments.

Genetics plays major role in when children take first steps

“The ability to walk requires practice and movement, and infants with higher activity levels or shorter attention spans may, on average, move about more, thus gaining more practice in movement, muscle strengthening and training, ultimately resulting in earlier walking onset,” the scientists said.

“Attention and activity levels may influence motor system training in young children, and this may relate to what we are observing at the level of common genetic variation.”

Their new study, published in Nature Human Behaviour, found that genetics accounts for about a quarter of the differences in when children take their first steps.

For years, researchers knew that environmental factors could influence when babies begin to walk, but this new finding shows that genetics also has a major impact. It suggests that, just like with other traits such as height, some children may naturally start walking earlier or later because of their genetic propensity.

The study also showed that relatively later onset of walking was influenced by some of the same genes involved in higher educational attainment.

Dr Anna Gui, one of the researchers at Birkbeck, University of London, said: “Until now, we didn’t understand what causes the wide differences between children in when they take their first step.

“Parents might often worry that walking early or late is a bad sign or that they have done something wrong. We see that genetics play a considerable role in influencing the timing of this milestone.”

Findings could influence public health policy

The authors said a greater understanding of the variability and causes of late walking would help many countries’ public health policy that aim to screen children for delay.

Knowing the genetic information that contributes to when children are likely to walk can sit alongside screening tools to help predict and identify clinically relevant conditions associated with early or delayed onset of walking, and avoid missing time for potentially beneficial physical training.

Walking is not just a key milestone in the development of a child, but it is connected in terms of genetic influences with many other important aspects of human development, the research team added.

Professor Angelica Ronald, senior researcher from the University of Surrey, said: “It is exciting to be able to discover the genes that influence when children learn to walk. Starting to walk independently is a major milestone for young children.

“We hope these new genetic findings can advance fundamental understanding about the causes of walking and be used to better support children with motor disorders and learning disabilities.

“While parents should still see their GP if they are concerned, a slightly later start is not always a sign of problems. There is a lot of variety in when children take their first step on their own.”