Ambidextrous children more likely to have language or scholastic problems and ADHD

It is estimated that ADHD affects between 3–9% of school-aged children and young people and a new study published in the journal Pediatrics, suggests that this includes a high proportion of children who are ambidexterous.

Dr Alina Rodriguez, and researchers at the School of Public Health at Imperial College London looked at prospective data from a cohort of 7,871 children from Northern Finland , 87 of whom were mixed-handed or ambidexterous. Using questionnaires, the researchers assessed the children when they reached 7 to 8 years of age and again at 15 to 16 years of age.

When the children were aged 8, the researchers asked parents and teachers to assess their linguistic abilities, scholastic performance and behaviour.

The adolescents' parents and the adolescents themselves completed follow-up questionnaires when they were 15-16 years of age, with the children evaluating their school performance in relation to their peers and the parents assessing their children's behaviour, on a questionnaire that is widely used to identify ADHD symptoms.

The study found that mixed-handed 7 and 8-year old children were twice as likely as their right-handed peers to have difficulties with language and to perform poorly in school.

When they reached 15 or 16, mixed-handed adolescents were also at twice the risk of having symptoms of attention deficit/hyperactivity disorder (ADHD). They were also likely to have more severe symptoms of ADHD than their right-handed counterparts.

The adolescents also reported having greater difficulties with language than those who were left- or right-handed. This is in line with earlier studies that have linked mixed-handedness with dyslexia.

Little is known about what makes people mixed-handed but it is known that handedness is linked to the hemispheres in the brain. Previous research has shown that where a person's natural preference is for using their right hand, the left hemisphere of their brain is more dominant.

Some researchers have suggested that mixed-handedness indicates that the pattern of dominance is not that which is typically seen in most people, i.e. it is less clear that one hemisphere is dominant over the other. One study has suggested that ADHD is linked to having a weaker function in the right hemisphere of the brain, which could help explain why some of the mixed-handed students in the study had symptoms of ADHD.

Because mixed-handedness is such a rare condition, the number of mixed-handed children in the study was relatively small, but the results are statistically and clinically significant. However, they should not be taken to mean that all children who are mixed-handed will develop ADHD; indeed most of the mixed-handed children in the study were not ADHD

Alina Rodriguez, Marika Kaakinen, Irma Moilanen, Anja Taanila, James J. McGough, Sandra Loo, and Marjo-Riitta Järvelin. Mixed-Handedness Is Linked to Mental Health Problems in Children and Adolescents. Pediatrics, Febuary 2010 (in press)

First published in 2010

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