A fascinating and robust new study has for the first time examined the association between teenage psychotic experiences and exposure to air pollution. The study strikingly found a significant correlation between higher rates of adolescent psychotic experiences and increased levels of urban air pollution.

For quite some time scientists have documented higher rates of mental illness in subjects living in urban environments. Most prior research has focused on understanding the potential social issues that could be causing these problems, with social isolation, crime and other factors long considered to be the primary causative agents of this strange correlation between urban living and psychotic episodes.

However, a research team from King's College London was inspired by a growing body of evidence linking air pollution to a variety of health issues, including depression, anxiety and even autism. So using new high-resolution measures of localized air pollution and a cohort of over 2,000 adolescents born in England and Wales deemed to be a nationally representative group, the scientists investigated this potential correlation.

The results were undeniably compelling with the data revealing a distinct link between higher levels of nitrogen dioxide (NO2) and nitrogen oxides (NOx) and higher incidences of psychotic episodes. For this study psychotic experiences were defined as episodes involving paranoia or delusions as evaluated through a detailed interview with a research worker. On average, around 30 percent of all young people report at least one instance of this kind of psychotic experience during adolescence. Air pollution was modeled using a new generation of modeling systems that have been effectively validated against ground-based measurements.

One of the big strengths of this study was its accounting for a variety of other factors that could be influencing rates of psychotic episodes. Significant adjustments were made to account for everything from family socioeconomic status and psychiatric history, to adolescent smoking, substance dependence or neighborhood crime and social conditions.

Evangelos Vassos, a researcher from King's College London who didn't work on this study, calls the work interesting and robust, noting in particular it is this rigorous adjusting for confounding factors that make it stronger than most correlation studies.

"For example, one can obviously think that people growing up in more polluted areas, probably come from lower socioeconomic status, and have higher exposure to substance use or traumatic experiences, both of which are associated with psychotic experience," says Vassos. "I noticed with interest that the association of pollution with psychotic experiences remained practically unchanged after adjustment for the above and other family and neighborhood factors."

The question of causality does hover over this study, however, the researchers are well aware this work does not imply a causal connection. Instead it can only strongly link the two factors, and the weight of the link uncovered is certainly powerful.

"We found that adolescent psychotic experiences were more common in urban areas," explains lead author on the study, Joanne Newbury. "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."

More work will be inevitably need to be done to explore specific neurological mechanisms that could connect these particular air pollutants to psychotic experiences, but this is an important first step in understanding whether our mental health is explicitly affected by pollution in urban environments. Sophie Dix, a researcher from the organization Transforming Mental Health, suggests this new study adds important insight into a serious modern problem.

"This study is significant because it provides a starting point with a possible link between pollution and psychosis, giving future research a platform to build upon," says Dix, who did not work on this new study. "Ruling risk factors in, or out, is helpful in determining how we can best address the issue."

The study was published in the journal JAMA Psychiatry.

Source: King's College London