Teenagers living in urban areas with higher levels of air pollution may be more likely to experience symptoms of psychosis, leading to the development of psychotic disorders and mental health problems later on in life.

Writing in JAMA Psychiatry, a team of UK-based researchers found that psychotic experiences are significantly more common in children with high exposure to nitrogen dioxide, nitrogen oxides, and small particulate matter even after accounting for genetic and socioeconomic risk factors for psychosis. Surprisingly, nitrogen dioxide and oxides accounted for 60 percent of the association for those who lived in an urban environment and experienced symptoms of psychosis.

“Children and young people are most vulnerable to the health impacts of air pollution owing to the juvenility of the brain and respiratory system,” said study author Frank Kelly in a statement. “Given that 70% of the world’s population will live in cities by 2050, uncovering the mechanisms linking the urban environment to psychosis should be an urgent health priority. Analyzing the health impacts of air pollution is a core component of King’s civic responsibility.”

To determine whether exposure to air pollution may be associated with adolescent psychotic experiences such as hearing voices or exhibiting intense paranoia, researchers analyzed data from the E-Risk study, a national database of environmental and genetic factors contributing to mental health issues in adolescents born in England and Wales. Interviewers asked 18-year-old participants questions such as “do you hear voices that others cannot” and “have you ever thought you were being watched, followed, or spied on?” The team then mapped the participant’s home address, along with two other frequently visited locations, against hourly air pollution models from the last year.

Prevalence of adolescent psychotic experiences according to exposure to air pollutants split by the highest quartile versus lower quartiles of exposure to each pollutant. JAMA Psychiatry

Almost one-third of the more than 2,000 respondents reported at least one psychotic episode within the last six years, most commonly those who had been exposed to the highest levels of air pollution.

An association between living in cities and psychotic experiences may partly be explained by higher levels of outdoor air pollution found in these urban places, but the study notes some worthy limitations. For starters, teenagers reporting psychotic experiences were not clinically verified that they were as such. Furthermore, pollution was only modeled for the year leading up to the interviews and may not account for early-life or cumulative exposure to air pollution. Lastly, the E-Risk study is a long-term longitudinal survey of twins and, though it provides a solid representation of the demographic, results could differ in non-twins. 

“We found that adolescent psychotic experiences were more common in urban areas. While the study could not show pollutants caused adolescents to have psychotic experiences, our findings suggest that air pollution could be a contributing factor in the link between city living and psychotic experiences,” said lead author Joanne Newbury.

Regardless, researchers say that global efforts to reduce air pollution levels to protect the mental and physical health of adolescents must be addressed in a rapidly urbanizing world. 

Air Pollution levels in rural, intermediate, and urban settings. Clear markers highlight the different World Health Organization (WHO) guidelines for these pollutants. JAMA Psychiatry

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