The number of words spoken in early childhood, a precursor sign of ADHD?

The number of words spoken in early childhood, a precursor sign of ADHD?

According to a new study, the number of words spoken by a child before the age of three could give an indication of a possible attention disorder. And the result is more surprising than it seems.

Are you impatiently awaiting your child’s first words? Be aware that they generally appear between 10 and 15 months, in what is called expressive vocabulary. Then the child gradually develops a richer vocabulary, from 100 to 600 words, and understands more, what is called receptive vocabulary. A path specific to each person, which of course includes individual differences. What is little known, however, is that these differences may be linked to variations in the genetic code stored in our cells. This is the subject that a team of scientists recently worked on.

Development associated with genetic information

The team of researchers from Radboud University in Nijmegen (Netherlands) wanted to examine the role of genetics in literacy (which includes spelling, reading and awareness of phonemes), cognition (intelligence general) and neurodevelopmental conditions, including attention-deficit/hyperactivity disorder (ADHD).

They thus studied 37,913 measures of vocabulary size reported by parents (English, Dutch, Danish) for 17,298 children of European origin and the genetic data of toddlers. Meta-analyses were carried out for:

  • Early expressive vocabulary (15 to 18 months);
  • Expressive vocabulary in the late phase (24 to 38 months);
  • Receptive vocabulary in the late phase (24 to 38 months).

Several genetic factors underlying vocabulary size in babies and toddlers have been identified. The team found that genetic associations with measures related to literacy, cognition, and ADHD varied across development.

  • Children’s word production was linked to reading and writing skills, such as spelling;
  • Links to cognition were only found for toddlers’ vocabulary scores aged 24 to 38 months, because they involve higher-level processing.

Children affected by ADHD express themselves more earlier

Regarding the link with a possible attention disorder, the analysis suggests that a greater risk of ADHD was genetically associated with a larger expressive vocabulary in babies aged 15 to 18 months. However, this trend reversed in toddlers aged 24 to 38 months, when vocabulary size was linked to cognition: a smaller number of words understood was associated with more ADHD symptoms.

“The genetic influences underlying vocabulary size change rapidly in less than two years during infancy. By adopting a developmental perspective, our findings provide insight into early etiological processes related to speech and language in health and troubles”concluded Beate St Pourcain, author of the study.