Exposure to air pollution leads to more severe mental illness, according to a new study.

The research follows concerns that the level of toxins in the air across London are “criminal” amid fears of the long term effect on children.

The latest study, published in the British Journal of Psychiatry and funded by the National Institute for Health Research (NIHR) Maudsley Biomedical Research Centre, analysed data from over 13,000 people.

The study suggests that reducing air pollution could have a significant positive effect on those diagnosed with psychotic and mood disorders, and could help to reduce the healthcare costs associated with the illnesses.

It found that people recently diagnosed with psychotic and mood disorders, such as schizophrenia and depression, used mental health services more often if they were exposed to traffic-related air pollution, signalling more severe symptoms.

Over the course of seven years, researchers at King’s College London, University of Bristol and Imperial College London analysed data from 13,887 people aged 15 years and over who had face-to-face contact with South London and Maudsley NHS Foundation Trust (SLaM) services between 2008 and 2012.

The researchers cross-referenced anonymous electronic mental health records, looking at the use of mental health services, with the quarterly average modelled concentrations of air pollutants at the residential address of the participants. Namely nitrogen dioxide and nitrogen oxides (NO2 and NOx) and fine and coarse particulate matter (PM2.5 and PM10).

People living in residential areas with higher rates of air pollution were more likely to use mental health services more frequently, it found.

Specifically, researchers found that, for every 3 micrograms per cubic meter increase in very small particulate matter and 15 micrograms per cubic meter increase in nitrogen dioxide over a one-year period, there was an increased risk of having an inpatient stay of 11% and 18% respectively.

In the same period, increases in very small particulate matter and nitrogen dioxide led to a 7% and 32% increased risk of requiring community-based mental healthcare respectively.

The results were replicated over the seven-year period.

The researchers estimated that, if the UK urban population’s exposure to PM2.5 was reduced to the World Health Organisation’s recommended annual limit (10 micrograms per cubic metre), the usage of mental health services could decrease by around 2%, saving tens of millions of pounds each year in associated healthcare costs.

Dr Ioannis Bakolis, senior lecturer in Biostatistics and Epidemiology at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN) at King’s College London and lead author of the study, said: “Our research indicates that air pollution is a major risk factor for increased severity of mental disorders.”

“It is also a risk factor that is easily modifiable which suggests more public health initiatives to reduce exposure such as low emission zones could improve mental health outcomes as well as reduce the high healthcare costs caused by long-term chronic mental illness.”

Over the course of seven years, researchers at King’s College London, University of Bristol and Imperial College London analysed data from 13,887 people aged 15 years and over who had face-to-face contact with South London and Maudsley NHS Foundation Trust (SLaM) services between 2008 and 2012.

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