Children and adults with attention deficit hyperactivity disorder, or ADHD, may be missing out on the best treatments because tests designed to spot the behavioural problem may actually cause the symptoms.

Reviews in the US of 63 ADHD studies found that demanding mental tasks or "boring" environments both led to "excess motor activity" in the two to five per cent of school-age children with ADHD, while in other environments their behaviour fell within social norms.

ADHD is diagnosed when patients display a group of behavioural symptoms including inattentiveness, hyperactivity and impulsiveness. Symptoms tend to be noticed at an early age, and up to five per cent of school-age children are thought to suffer from the condition.

Those with ADHD, who include The Voice judge Will.i.am, may also have sleep and anxiety disorders.

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READ MORE: • Do you have adult ADHD?

Of the new findings, lead author Dr Michael Kofler, from the Children's Learning Clinic in Florida, said: "It seems pretty clear at this point that hyperactivity isn't this random, purposeless behaviour where kids with ADHD are always on the go or driven like a motor. It could be that in certain environments they are becoming hyper."

The findings could also mean that some children who have ADHD do not receive a diagnosis because their hyperactivity occurs only in certain situations.

Dr Kofler added: "What we are trying to do is find the specific cognitive processes that seem to evoke hyperactive behaviour because that is where we are going to try to develop more targeted psychotherapeutic treatments."