Doctors have found a "significant" link between asthma and attention deficit hyperactivity disorder (ADHD) in children.
Dr Samuele Cortese, of the University of Southampton, who led the research, says the results suggest a "possible role of allergic mechanisms in ADHD" and could lead to changes in clinical management of the two conditions.
The study, by an international team of researchers, has been published in the journal Lancet Psychiatry.
Dr Cortese, associate professor in psychology and medicine, said: "By combining a comprehensive analysis of available studies with a new large population-based study, we provided rigorous evidence supporting a significant association between ADHD and asthma.
"Mental health practitioners as well as clinicians involved in the care of respiratory diseases should be aware of this association, which might help to reduce delay in the diagnosis of both ADHD and asthma.
"Future research should aim to understand the mechanisms underlying this association, including possible common inflammatory alterations."
The study examined two sources of data for the research - one involving 49 pre-existing datasets and the other from a population-based study in Sweden.
A university spokesman said: "According to the analysis of the 49 datasets, the prevalence of asthma was 16.9 per cent in individuals with ADHD and 11.5 per cent in those without.
"The prevalence of ADHD was 8.8 per cent in individuals with asthma and 5.6 per cent in those without.
"Results were similar in the population-based study, where the prevalence of asthma was significantly higher in individuals with ADHD than in those without (24.8 per cent vs 16.1 per cent).
"Additionally, the prevalence of ADHD was significantly higher in individuals with asthma than in those without (5.5 per cent vs 3.3 per cent)."
