"This research had a number of limitations, including the fact that only 87 children were ambidextrous. Also, rates of developmental and mental health problems were based on the results of questionnaires given to the children, parents and teachers and not on professional assessments. Without formal assessments it is not possible to determine whether the children truly had conditions like ADHD."

http://www.nhs.uk/news/2010/01January/Pages/ambidextrous-lin...