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From an article by John Gever at MedPage Today:
An online report in Pediatrics details findings that indicate that ambidextrous 5-year-olds are more likely to develop attention deficit-hyperactivity disorder symptoms later on, compared with right- and left-handed children.
The authors feel that brain morphology and neural circuitry associated with handedness also affects cognitive and behavioral function.
The study was done by a team of Swedish researchers led by Alina Rodriguez, PhD, of Uppsala University in Sweden.
This was a longitudinal study of 7,871 children, born in 1986, in northern Finland. There were 87 mixed-handed children, 632 left-handed, with the remainder right-handed.
Rodriquez and her colleagues found that when these children were tested at age 8, teachers were about twice as likely to find hyperactivity in the mixed-handed children, as compared with those who were right-handed.
In addition, the learning and behavioral problems persisted into adolescence.
Similar increases were found in rates of teacher assessments of probable psychiatric disturbance and in overall school performance (as well as parental reports of language problems) in ambidextrous children.
Evaluated at age 16, those children classed as mixed-handed were more than three times as likely to suffer inattention or a combination of inattention and hyperactivity-impulsivity, relative to right-handed 16-year-olds.
And self-reported problems in Finnish language and math classes were also significantly more common in the mixed-handed young people.
Note: these effects were NOT seen in left-handed children.
The authors write that
“Mixed-handedness can be used as a marker of risk for difficulties and warrants additional evaluation.”
Rodriquez and colleagues say results support the hypothesis that brain abnormalities stemming from before birth underlie what they called “atypical lateralization” and subsequent learning and behavior problems.
They add that recent neuropsychological work related to patterns of brain organization and function corroborates the findings.
They cite research indicating that ADHD is associated with left-side motor deficits, apart from hand preference, as well as reduced attention to visual stimuli on the left versus the right side.
These observations suggest weaker right hemisphere function.
Other studies have suggested that neural transmission can be assymetric between hemispheres.
“These studies together highlight the possible interconnection among mixed-handedness, neurotransmitter dysfunction in the right hemisphere, and ADHD symptoms.”
The study was funded by the Academy of Finland, Sigrid Julius Foundation, Thula Institute, University of Oulu, Finland, and the National Institute of Mental Health. Rodriquez was also supported by VINMER, with no potential conflicts of interest reported.
sole source: article at http://www.medpagetoday.com artile by John Gever on 1/25/2010.
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