Children who live in areas with higher air pollution when they are younger, according to research, are significantly more likely to experience severe depression by the age of 18 years.
In a first analysis of how general pollutants affect adolescent mental health, scientists have found that young people are three to four times more likely to be depressed at the age of 18 when exposed to more dirty air at the age of 12. is a greater risk factor than physical abuse in increasing the risk of depression in adolescents.
Scientists have said that their findings are particularly significant because 75% of mental health problems begin in childhood or adolescence when brains develop rapidly. The work also suggests a link between toxic air and antisocial behavior, but more work is needed to confirm this. This year, a larger study is expected.
"High levels of air pollution are not beneficial to you, and especially to your children, whether physical or mental," says Helen Fisher of Kings College London, who conducts research. "It is sensible to try to avoid areas with the highest levels of air pollution. We should really push for local and national governments to reduce these levels."
The study, published in Psychiatry Research, combined information from a group of children in London with data on high levels of pollution.
Of the 284 children surveyed, it was found that those who lived in the highest 25% of the most polluted areas at the age of 12 are three to four times the likelihood of depression at the age of 18 compared to those who live in 25% of the least polluted areas. Compared to previous work, it was found that children who suffer from physical abuse are one and a half times more likely to develop depressive disorders.
Researchers have taken into account other factors that could affect mental health, such as family history of mental illness, income levels, bullying and smoking. They also looked at levels of anxiety and ADHD, but found no link to air pollution.
An increase in the risk of antisocial behavior was three to five times higher. But unlike the relationship to depression, the result was not statistically significant, potentially because the number of adolescents in the study that was behaving badly was low.
Compared to physical health, the effect of air pollution on mental health was relatively little studied. Adult research has so far produced conflicting results, although there is strong evidence that air pollution can result in "significant reductions in intelligence".
The study was not designed to investigate the cause of depressed adolescent suffering, but Fisher said the inflammation caused by toxic contamination was likely: "We know that pollutant particles are small enough to cross the blood brain barrier [and] we know that there are great connections between brain inflammation and the development of depressive symptoms. "
She said children and adolescents are particularly vulnerable. "Their brains are developing, hormonal things are changing tremendously and are subject to many stressful things," such as shaping their relationship with the world as well as testing and looking for work, she said.
Fisher said further research is important because air pollution solutions will probably be less complex than other factors that cause psychiatric damage. "If we can really understand what's going on, we have the potential to hit early and do something with that," she said.
"This study highlights the dangers of air pollution among adolescents in Great Britain, especially those living in urban areas", where mental health problems are higher, said Robin Russell-Jones, a public health doctor.
Nitrogen dioxide pollution levels are at illegal levels in most of the UK's urban areas, and small particle pollution exceeds the World Health Organization's guidelines in many places. The government accepts that the dirty air shortens lives and damages children, but its latest road traffic action plan has been described as "pitiful" lawyers in the field of the environment.
Professor Chris Griffiths, founding member of the Doctors Against Diesel campaign, said: "Further studies are needed, but the urgency of drastic reductions in exposure of young people to toxic air pollution remains."
"The apparitions are really shocking and sorrowful and show how critical it is that this public health crisis is properly addressed," said Jenny Bates at Friends of the Earth.
Rebecca Daniels at Medact's health charity said: "Government's response is greatly lacking – we need a robust and comprehensive clean air policy, including a drastic reduction in the number of polluting vehicles on our roads."