In the long-term, breathing polluted air leads to a greater risk of depression, according to two major new studies, adding to growing evidence of the harmful effect of pollution on mental health.
The first study, published last week in the journal JAMA psychiatry, studied a population of about 390,000 people in the UK over a period of 11 years. The levels of pollution they were exposed to were estimated based on their home address.
The researchers looked at levels of fine particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2) and nitric oxide (NO) – pollution caused by fossil fuel power stations and road traffic, among others.
“Long-term exposure to multiple pollutants was associated with an increased risk of depression and anxiety,” the researchers concluded.
The observed risk was non-linear, meaning that it was strongly increased above a relatively low concentration level and then tended to stagnate thereafter.
“Knowing that air quality standards in many countries still far exceed the latest World Health Organisation (WHO) recommendations of 2021, stricter pollution standards or regulations should be put in place,” the study authors wrote.
A second study, published on Friday in JAMA Network Open, focused on the effect of fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ozone (O3) on people over the age of 64.
The aim was to study the consequences of air pollution on the onset of depression late in life.
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The work used a database from Medicare, the public health insurance for the elderly in the US, and studied a population of about 8.9 million people, including about 1.5 million cases of depression.
The results again show a strong association between pollution and depression, particularly when looking at levels of fine particles and nitrogen dioxide for disadvantaged populations.
This association could be explained by the observed link between high concentrations of pollutants and inflammation in the brain, the two studies said.
“There is a strong emerging link between inflammation and depression,” commented Oliver Robinson, professor of neuroscience and mental health at University College London, who was not involved in the research.
This work “adds to the growing body of evidence that we should be concerned about the effects of pollution on mental health, in addition to the more obvious links” with respiratory disease, he added.
