A new study in South Korea suggests that air pollution doesn't just make it hard to breathe - it may also push people to take their own lives.
Chang Soo Kim of Yonsei University in Seoul and his colleagues found that suicides were more common in the two days following a spike in pollution.
According to The New Scientist, the results revealed that people were 9 per cent more likely to kill themselves following a spike in pollution rising across the middle 50 per cent of recorded values.
For people with cardiovascular disease, the increase was almost 19 per cent.
A decade later, the researchers show that suicides were more than twice as common among those with asthma - and the more severe their symptoms, the higher the risk.
David Callahan at the Centers for Disease Control and Prevention in Atlanta, Georgia, says that people with depression are known to be worse at managing chronic diseases by taking prescribed drugs and following other medical advice - potentially causing a spiral of physical and mental deterioration.
Kim suggested that PM10s may also cause nerve inflammation, affecting mental health through a direct biological mechanism.
The study is published in American Journal of Psychiatry.