Children who suffer with asthma and allergies may have an increased risk of developing ADHD (attention deficit hyperactivity disorder), a new study suggests.

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

According to Dutch and US scientists, the number of children being diagnosed with ADHD, asthma and allergies is on the increase and recent research suggests there may be a link between the three conditions.

They decided to investigate this further. They looked at almost 900 boys with ADHD and more than 3,500 boys without the condition.

They found that among the children with ADHD, at least one in three had asthma and one in three had an allergy of some sort. These were higher than the figures for those without ADHD.

In other words, boys with a history of asthma or allergies were found to have an increased risk of ADHD.

"ADHD, a chronic mental health disorder, is most commonly found in males, while asthma is also more common in young boys than girls. We found there is an increased risk of ADHD in boys with a history of asthma and an even stronger risk associated with milk intolerance," the scientists explained.

They said that more research is needed to discover why this link exists, but they suggested that medications used to treat asthma and allergies may be partly to blame.

However, according to Dr Gailen Marshall, editor-in-chief of the journal, Annals of Allergy, Asthma & Immunology, which published the findings, ‘medications for these conditions far outweigh the risks and can be life-saving in some conditions.'

She insisted that treatment ‘should not be stopped', unless advised by an appropriate health professional.

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