A new study has shown that ADHD does not ‘go away' when a person reaches adulthood and that those affected are more likely to suffer from mental health problems, such as depression.

ADHD is a behavioural disorder, the main symptoms of which include inattention, impulsivity and hyperactivity. It can often lead to disruptive behaviour in the classroom and as a result, is often first identified in school. Up to one in 20 children in Ireland is affected.

According to US scientists, their study is the first large population-based study that has followed children with ADHD into adulthood. Most other studies have been small and have tended to focus on those with more severe forms of the condition, rather than just a cross section of the population.

The study followed the progress of over 5,700 children born between 1976 and 1982. Almost 370 of these were diagnosed with ADHD.

The study found that almost one in three of the children with ADHD still had the condition as an adult. Furthermore, at least half of those who had ADHD as a child had at least one other psychiatric disorder as an adult, including anxiety, depression and substance dependence.

Among those who still had ADHD as adults, eight in 10 had at least one other psychiatric disorder compared to just under half of those who only had the condition as a child and one in three of those who never had it.

"We suffer from the misconception that ADHD is just an annoying childhood disorder that's overtreated. This couldn't be further from the truth. We need to have a chronic disease approach to ADHD as we do for diabetes. The system of care has to be designed for the long haul," explained lead investigator, Dr William Barbaresi, of the Boston Children's Hospital.

He noted that these findings may actually underestimate the long-term detrimental effects of ADHD, as the group involved were largely middle-class with good access to healthcare and education.

"One can argue that this is potentially a best-case scenario. Outcomes could be worse in socioeconomically challenged populations," he suggested.

Dr Barbaresi advised the parents of affected children to ensure that they remain in good quality treatment as they enter their teens. These young people should also be assessed for conditions such as depression, anxiety and addiction.

He added that the findings show the need to ‘greatly improve the long-term treatment of children with ADHD and provide a mechanism for treating them as adults'.

Details of these findings are published in the journal, Pediatrics.