Higher Risk of ADHD in People Who Are Ambidextrous
Ambidextrous, or mixed-handed, is the "ability of being equally adept with each hand." [Nationmaster.com Encyclopedia] Those born ambidextrous are rare, most of the time this is learned. The majority of people that are ambidextrous were originally left handed and learned to use their right hand, possibly because of social and cultural pressures. Many people, even though able to use both hands equally, still have a dominant hand. Still, only approximately 1% of the population is ambidextrous.
We have long sought answers to why some people are right-handed and some are left-handed and to explain the differences. For example, many people associate creativity with being left-handed, although there are many people that are right-handed, or mixed-handed, who are just as creative. I have heard some people indicate that people with ADHD are more often left-handed, but science does not seem to back up this claim.
A recent study, [Pediatrics, 2010] however, indicated that children who are ambidextrous may be at higher risk for:
Mental health issues, including ADHD
Researchers aren't sure why this is so, or even what causes mixed-handedness, but hope the results may help teachers better identify students at risk for academic problems. It is important to note that not all children that are ambidextrous will develop mental health issues, ADHD or have problems in school. The study indicated a higher percentage of these children exhibited such difficulties, but was not a precursor to academic problems.
The study looked at 8000 children in Northern Finland at both 7-8 years of age and 15-16 years of age. Language abilities, overall academic performance and behavior issues were examined.
Specific Results of the Study
At the age of 7 or 8:
Left-handed children were 30% more likely to have difficulties in math.
Mixed-handed children were 90% more likely to have difficulties in math.
Mixed-handed children were twice as likely to have language difficulties.
Mixed-handed children were twice as likely to have poor academic performance.
At the age of 15-16:
Mixed-hand teens were twice as likely to be diagnosed with ADHD and those with ADHD had more severe symptoms than right-handed teens with ADHD.
Mixed-handed teens indicated they had more problems with language skills.
We know that a person that is right-handed has a more dominant left brain and vice-versa. This, however, does not explain how a brain would function in someone who uses both hands. Lead researcher in the study, Alina Rodriguez of the Imperial College London, in an interview with LiveScience, indicated, "All we can say from this is that they have an atypical brain lateralization; that just means the brain circuitry and function is likely to differ from the normal pattern, seen in right-handed individuals"
The results may indicate that the right hemisphere of the brain may not function the same in those that are right-handed and those that are mixed-handed. ADHD has been associated with difficulties in processing information with the right hemisphere and this may be why the risk is much higher.