Using a national database of children born between 1990 and 1999, the study, published in Archives of Pediatrics and Adolescent Medicine, recorded 4,637 diagnoses from ages three to 13 for autistic disorders, hyperkinetic disorder, obsessive-compulsive disorder and Tourette syndrome.
While previous studies had found an increase in autism, this was the first to show significant rises in hyperkinetic disorder and Tourette syndrome.
Chief researcher Hjordis Osk Atladottir said, 'This puts the increase in incidence of autism into perspective since we display a similar increase for Tourette syndrome and hyperkinetic disorder. Further studies are needed before anything can be concluded.'
Theories for the increase include environmental and genetic factors, or improvements in diagnosing such disorders.
The study is published in this month's issue of ends