CHICAGO (Reuters) — A look at all children born in Denmark over a recent 10-year period found not only marked increases in autism as expected but also in hyperactivity and Tourette’s syndrome, a study said on Monday.The report from Denmark’s University of Aarhus did not delve into what had caused the increases.

It said that numerous earlier studies had reported notable increases in recent years in the number of children being treated for autism, which is marked by isolating social and language abnormalities and repetitive patterns of behaviour.

Some of its increase may be related to heavier scrutiny of children for the problem or perhaps an expanded definition of what encompasses autism, health experts have said previously.

But Thursday’s study published in the Archives of Pediatrics & Adolescent Medicine said the upward trends in reported autism diagnoses may be part of a broader pattern in childhood neuro-psychiatric illness.

It looked at medical records involving all 669,995 children born in Denmark between 1990 and 1999, tracking autism spectrum disorder, which includes autism and milder developmental disorders; hyperactivity; Tourette’s syndrome, characterised by uncontrollable vocal or motor behaviours; and obsessive-compulsive disorder.

In all 4,367 of the children had been diagnosed with one or more of the problems by 2004, the study said.

Hyperactivity, Tourette’s syndrome and various forms of autism all increased significantly during the time period studied but obsessive-compulsive disorder did not, the report said.

“It is difficult to explain why obsessive-compulsive disorder was the only disorder displaying another pattern,” the authors said.

While the study did not address the causes of the increases in the other three problems “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 concluded.