An ADHD sufferer. The condition is believed to affect between two and five per cent of school-age children / Time Life Pictures/Getty Images

ADHD is the most common behavioural disorder in the UK

Children with ADHD who have higher IQs are more likely to "grow out" of the condition as teenagers than those with average IQs.

It is thought the results could help scientists understand  the best ways to help the development of interventions for those with attention deficit hyperactivity disorder, according to research research by King’s College London.

Around one in 20 children have ADHD. The condition persists into adolescence and early adulthood for around two-thirds of individuals.

The research examined 110 young people with ADHD and 169 controls over a six year period.

They tested IQ, attention, levels of drowsiness and reaction time in children and did follow-up testing over an average of 6.6 years.

It was found that the cases with ADHD which had gone into remission had a higher IQ than those whose ADHD persisted.

They also performed better on cognitive and EEG tests measuring attention and levels of drowsiness.

"We try to measure the underlying processes at the cognitive and brain level - so to measure for example inattention in the brain directly", co-author Dr Jonna Kunsti said.

It is not yet known for sure if inattention at the brain level causes the behavioural symptoms associated with ADHD or whether improving attention and focus would help lead to remission.

"We showed which cognitive and brain processes improve when ADHD improves, but we did not test directly in this study if their relationship is causal," Dr Kuntsi said.

"Our findings raise this as a possibility." However, further studies would be needed to discover if cognitive training and neurofeedback could help more children to "grow out" of ADHD.

According to the NHS website, ADHD is the most common behavioural disorder in the UK and most children are diagnosed between the ages of six and 12.

The symptoms usually improve with age but many adults continue to experience problems also.

"Clinicians and teachers should be made aware that children with ADHD who also have lower general cognitive ability are particularly at risk for their ADHD persisting over time, and so they may need extra help," Dr Kuntsi who works at the Institute of Psychiatry, Psychology & Neuroscience at King's College said.