Air pollution can trigger depression and may even lead to suicide, warns a new study.

Researchers found people exposed to high levels of air pollution are more likely to have suicidal thoughts and suffer from depression.

Average pollution levels in cities around Britain exceed the World Health Organisation’s (WHO) recommended limit.

Study lead author Dr Isobel Braithwaite, of University College London (UCL), said: “We already know that air pollution is bad for people’s health, with numerous physical health risks ranging from heart and lung disease to stroke and a higher risk of dementia.

“Here, we’re showing that air pollution could be causing substantial harm to our mental health as well, making the case for cleaning up the air we breathe even more urgent.”

Pollution levels refer to the number of harmful airborne particles, and should not exceed ten microgrammes per metre cubed.

The researchers pooled 25 studies looking at the effects of pollution on mental health and compared the results.

They found people exposed to high pollution levels for long periods face a 10 per cent higher risk of depression.

Dr Braithwaite said: “We found quite consistent results across the studies we reviewed that analysed the relationship between long-term air pollution exposure and depression, even after adjustment for many other factors which could explain the association.

“The association seems to be similar in magnitude to those that have been found for some physical health impacts of particulate matter, such as all-cause mortality.”

They also found the risk of suicide rose when pollution levels peaked.

Coarse particulates

A short-term rise in “coarse particulates” in particular was linked to a two per cent rise in suicide risk.

Dr Braithwaite said: “We know that the finest particulates from dirty air can reach the brain via both the bloodstream and the nose, and air pollution has been implicated in increased neuroinflammation, damage to nerve cells and to changes in stress hormone production, which have been linked to poor mental health.

The team believes meeting the WHO’s guidelines could reduce the risk of depression among UK residents by over two per cent.

Around 20 per cent of adults in the UK suffer from anxiety or depression, according to the Mental Health Foundation.

Study senior author Dr Joseph Hayes, also of University College London, said: “Our findings correspond with other studies that have come out this year, with further evidence in young people and in other mental health conditions.

“While we cannot yet say that this relationship is causal, the evidence is highly suggestive that air pollution itself increases the risk of adverse mental health outcomes.”

Dr Hayes added: “A lot of what we can do to reduce air pollution can also benefit our mental health in other ways, such as enabling people to cycle or walk rather than drive, and enhancing access to parks, so this adds support to the promotion of active travel and urban green spaces.”

The findings were published in the journal Environmental Health Perspectives.

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