Dispensed medication for psychiatric diagnosis can be related to air pollution concentrations, researchers from Umea University in Sweden said.

They studied the correlation between exposure to air pollution in residential areas and childrens' and adolescents' psychiatric health.

The study was performed by looking at register-based data, where dispensed medications of all Swedes are registered, together with Swedish National Register data of air pollution concentrations.

The entire population under 18 in four countries in Sweden was studied.

The results show that air pollution increased the risk of having dispensed medication for at least one psychiatric diagnosis for children and adolescents, researchers said.

The risk increased by nine per cent with a 10 microgramme per cubic metre increased concentration of nitrogen dioxide even after socioeconomic and demographic factors were taken into account, they said.

"The results can mean that a decreased concentration of air pollution, first and foremost traffic-related air pollution, may reduce psychiatric disorders in children and adolescents," said Anna Oudin from Umea University.

The findings were published in the journal BMJ open.