Children who lived in areas with higher air pollution when younger are significantly more likely to develop major depression until age 18, according to the survey.
In the first analysis of how air pollutants affect teenagers' mental health, researchers found that young people were three to four times more depressed at age 18 if they had been exposed to dirtier air by age 12. is a greater risk factor than physical abuse to increase the risk of depression in adolescence.
Scientists said their findings are particularly significant because 75 percent of mental health problems begin in childhood or adolescence when the brain is developing rapidly. The work also suggests a link between toxic air and antisocial behavior, but more work is needed to confirm this. A larger study is expected later this year.
"High levels of air pollution are not good for you, and particularly for your children, whether it's physical or mental health," said Helen Fisher, of Kings College London, who led the research. "It is wise to try to avoid areas with the highest levels of air pollution. We really should be pushing for local and national government to reduce those levels. "
The study, published in the journal Psychiatry Research, combined information from a group of children in London with high resolution data on air pollution levels.
Of the 284 children studied, those living in the 25% of the most polluted areas at age 12 were three to four times more likely to be depressed at age 18, compared to those living in the least polluted areas of 25%. In comparison, previous work has shown that children who are physically abused are half as likely to develop depressive disorders.
The researchers took into account other factors that could affect mental health, such as family history of mental illness, income level, bullying and smoking habits. They also looked at levels of anxiety and ADHD, but found no connection with air pollution.
The increased risk of antisocial behavior was three to five times higher. But unlike the link to depression, the result was not statistically significant, potentially because the number of adolescents in the study who misbehaved was small.
Compared with physical health, the effect of air pollution on mental health has been relatively little studied. Adult research so far has produced conflicting results, although there is strong evidence that air pollution can result in a "significant reduction in intelligence."
The study was not designed to investigate the cause of teen depression, but Fisher said the inflammation caused by toxic pollution was more likely: "We know that the pollutant particles are small enough to cross the blood-brain barrier. [and] we know that there are great links between inflammation in the brain and the development of depressive symptoms. "
She said children and adolescents are particularly vulnerable. "Their brains are developing, hormonally, things are changing tremendously, and they are exposed to many stressful things," such as forming their relationship with the world, as well as examinations and job search, she said.
Fisher said more research is important, since tackling air pollution is likely to be less difficult than other factors that cause psychiatric damage. "If we can really understand what's happening, then we have the option to intervene early and do something about it," she said.
"This study emphasizes the dangers of air pollution to the UK teen population, especially those living in urban areas," where mental health problems are greatest, said Robin Russell-Jones, a public health doctor.
Nitrogen dioxide pollution levels are at an illegal level in most urban parts of the UK, and small particle pollution exceeds World Health Organization guidelines in many places. The government accepts dirty air shortens lives and harms children, but its latest road pollution action plan has been described as "deplorable" by environmental lawyers.
Chris Griffiths, a founding member of the Doctors Against Diesel campaign, said: "More studies are needed, but the urgency to drastically reduce youth exposure to toxic air pollution remains."
"The revelations are really shocking and sad and they show how critical this public health crisis is treated properly," said Jenny Bates of Friends of the Earth.
Rebecca Daniels of the Medact charity said: "The government's response is severely lacking – we need robust and comprehensive clean air policies now, including a drastic reduction in the number of polluting vehicles on our roads."