Children who are mixed-handed, or ambidextrous, are more likely than right- or left-handed children to have mental health, language and scholastic problems in childhood.

Researchers from Imperial College London and other European institutions suggest that their findings may help teachers and health professionals identify children who are particularly at risk.

Around one in every 100 people is mixed-handed. The study looked at nearly 8,000 children, 87 of whom were mixed-handed, and 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.

Handedness is linked to the hemispheres in the brain, but little is known about what makes people mixed-handed. Previous research has shown that when a person's natural preference is for using their right hand, the left hemisphere of their brain is dominant. Some researchers have suggested that mixed-handedness indicates the pattern of dominance is different from that typically seen in most people -- that is, it is less clear that one hemisphere is dominant over the other. One study suggesting that ADHD is linked to having a weaker function in the right hemisphere of the brain could help explain why some of the mixed-handed students in this study had symptoms of ADHD.

Lead researcher Dr Alina Rodriguez, from the School of Public Health at Imperial College London, was quoted as saying, "Mixed-handedness is intriguing -- we don't know why some people prefer to make use of both hands when most people use only one. Our study is interesting because it suggests that some children who are mixed handed experience greater difficulties in school than their left- and right-handed friends. We think that there are differences in the brain that might explain these difficulties, but there needs to be more research.”