A comprehensive Danish study has found that over a 10-year period there has been in Denmark a substantial rise in cases in children of autism, hyperactivity and Tourette's syndrome.
The study carried out by researchers at Denmark's University of Aarhus did not examine the possible causes of the increased numbers.
Apparently a number of earlier studies had also reported notable increases in recent years in the number of children being treated for autism, which could say experts in some respects be due to better scrutiny, improved diagnostic techniques and a broader definition of the disorder, or possibly due to environmental factors.
Autism is characterised by social isolation, language abnormalities and repetitive and compulsive patterns of behaviour. Tourette's syndrome is characterized by uncontrollable vocal or motor behaviours.
But the Danish study says the upward trends in reported autism diagnoses may be part of a broader pattern in childhood neuro-psychiatric illness.
Lead researcher Hjordis Osk Atladottir and colleagues examined medical records involving all 669,995 children born in Denmark between 1990 and 1999.
They tracked the whole spectrum of disorders including autism spectrum disorder, which includes autism and milder developmental disorders; hyperactivity and Tourette's syndrome, and obsessive-compulsive disorder.
Of the total number, 4,367 of the children had been diagnosed with one or more of the problems by 2004, with significant increases seen in hyperactivity, Tourette's syndrome and various forms of autism.
The authors say it is clear that the number of children with neuropsychiatric disorders and their families in need of support and services has been growing in recent years.
The study is published in the Archives of Pediatrics & Adolescent Medicine.