A new study, published in the journal JAMA Psychiatry, provides a potential explanation for why growing up in urban settings is a risk factor for psychosis.
In this study, air pollution exposure was associated with increased odds of psychotic experiences in adolescence, which partly explained the association between urban residency and adolescent psychotic experiences. Image credit: Johannes Plenio.
Psychotic experiences, such as hearing voices and intense paranoia, are less extreme forms of symptoms experienced by individuals with a psychotic disorder like schizophrenia.
While psychotic experiences are more common in adolescence than adulthood, young people who report psychotic experiences are more likely to go on to develop psychotic disorders, as well as a range of other mental health problems and suicide attempts.
“Psychotic disorders are difficult to treat and place a huge burden on individuals, families, health systems and society more broadly,” said study senior author Dr. Helen Fisher, from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London, UK.
“By improving our understanding of what leads to psychotic experiences in adolescence, we can attempt to deal with them early and prevent people from developing psychotic disorders and other serious mental health problems.”
Dr. Fisher and co-authors found that psychotic experiences were significantly more common among adolescents with the highest exposure to nitrogen dioxide (NO2), nitrogen oxides (NOx), and very small particulate matter (PM2.5), even after accounting for known risk factors for psychosis.
NO2 and NOx together accounted for 60% of the association between living in an urban environment and having adolescent psychotic experiences.
“We found that adolescent psychotic experiences were more common in urban areas,” said study first author Dr. Joanne Newbury, also from King’s College London.
“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.”
The scientists used data from the E-Risk study, which comprises 2,232 children born in England and Wales.
Young people were assessed for psychotic experiences in private interviews at age 18, responding to questions such as ‘do you hear voices that others cannot?’ and ‘have you ever thought you were being watched, followed or spied on?’.
The data on psychotic experiences were linked with hourly estimates of air pollution at 65 x 65 feet (20 x 20 m) grid points throughout the UK.
Combining home addresses with two additional locations where the young people spent substantial amounts of time at age 17 meant the researchers could accurately model their exposure to air pollution over the space of a year.
“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 co-author Professor Frank Kelly, also from King’s College London.
“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.”
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Joanne B. Newbury et al. Association of Air Pollution Exposure With Psychotic Experiences During Adolescence. JAMA Psychiatry, published online March 27, 2019; doi: 10.1001/jamapsychiatry.2019.0056
