We know dirty air is bad for our bodies,听causing the equivalent of millions of deaths worldwide each year, making it a bigger killer than smoking. But could air pollution be bad for our minds too?
A study has found psychotic experiences, which can involve hearing or seeing something that others don鈥檛, are more common among teenagers in the UK鈥檚 most polluted areas.
However, the association doesn鈥檛 mean that breathing in air pollution leads to psychosis in teenagers,听because there could be other explanations. The study doesn鈥檛 show causation, says Helen Fisher of King鈥檚 College London, one of the study鈥檚 authors.
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Fisher and her colleagues found that 30 per cent of a group of 2000 18-year-olds听reported having at least one psychotic experience in their teens 鈥� other research on young adults has reported similar figures.听However, when the teenagers鈥� addresses were mapped against air pollution, those in areas with higher pollution were more likely to have reported a psychotic experience.
In areas with the highest levels of nitrogen oxides听(NOx)听鈥� pollutants听produced by diesel cars 鈥� 12 teens reported psychotic experiences for every 20 teens who didn鈥檛, with the number falling to听seven for every 20 in cleaner areas.
It听isn鈥檛 known听how air pollution could be linked to psychotic experiences. One speculative mechanism put forward by the team is of a cumulative build-up of pollutants directly influencing the brain.
Studies have linked air pollution with inflammation and degeneration in the frontal cortex and the part of the brain that gives us our sense of smell, the olfactory bulb. Inflammation of the brain .
A simpler explanation could be that it is not the dirty air itself, but the noise from the cars听emitting pollution. Noise pollution听can increase听stress and disrupt sleep, two factors associated with psychotic experiences.
Cutting听through the smog
鈥淭here is no evidence that pollution necessarily causes psychosis, or whether this is one of many factors or acting in isolation,鈥� says Sophie Dix at mental health charity MQ. But听the study provides a starting point for a possible link between pollution and psychosis, she says.
There is an emerging body of research looking at possible links between air pollution and mental health. For example,听听has been found听between polluted areas and Swedish children being given medication for psychiatric disorders.
There is a compelling case听for听further investigation听into听toxic air鈥檚听potential connection to听mental health, says Stefan Reis at the Centre for Ecology and Hydrology in the UK.
But there is limited evidence so far, says Fisher. 鈥淚t鈥檚 really preliminary. We don鈥檛 know very much.鈥�
Fortunately, the world doesn鈥檛 need to wait until any link is proven between air pollution and mental health to act on what we pump into the air, because we know so much about air听pollution鈥檚 harmful听physical impacts. Tiny particulate matter can penetrate deep into the lungs and bloodstream,听, including infections and听aggravating听asthma. It has also been associated with low weight and premature babies.
鈥淭here鈥檚 a huge weight of evidence on the physical effects,鈥� says Fisher.
JAMA Psychiatry
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