Newbury J, Arseneault L, Beevers, S, et al. Association of air pollution exposure with psychotic experiences during adolescence [published online ahead of print March 27, 2019]. JAMA Psychiatry.
To assess the association between adolescent psychosis and air pollution and to further determine if this could be an underlying etiology for increased adolescent psychosis rates in urban dwellings.
Population-based cohort study from the UK’s Environmental-Risk Longitudinal Twin Study
The study included 2,232 adolescents, followed from birth to age 18 as part of the Environmental-Risk Longitudinal Twin Study. Participants were born between January 1, 1994 and December 4, 1995 and were nationally representative in terms of geographic and socioeconomic status among UK families.
Of the original participants, 2,066 (92.6%) took part in the 18-year follow-up; 2,063 of those who were followed up provided data on psychotic experiences. Of these, 52.5% participants were female and 47.5% were male.
Study Parameters Assessed
Data gathered included air pollution exposure, participants’ urbanicity, and the occurrence of psychotic events between the ages of 12 and 18.
Participants were initially assessed at age 5, and then again at ages 7, 10, 12, and 18. During the final assessment at age 18, researchers conducted private interviews with each participant to evaluate possible occurrence of 13 various psychotic experiences since age 12. Seven items were related to delusions and hallucinations, and 6 items were related to prodromal psychosis experiences. Each experience was coded as present (2), probably present (1), or not present (0), then summed and represented on an ordinal scale and verified by healthcare professionals.
The implications of this study are important not only for practitioners who are treating adolescents but also those who primarily focus on adult health, given that early psychotic episodes are a risk factor for adult psychoses and warrant early intervention.
Air pollution exposure was measured using pollution generation estimates from home addresses of participants and 2 commonly visited locations (often school, work, or shops) in the year 2012, 1 year before interviews with participants commenced. Pollutants measured included nitrogen dioxide (NO2), nitrogen oxides (NOX), and particulate matter (PM2.5 and PM10) from inorganic aerosols, carbonaceous aerosols, and dusts. Measurements were made with high-resolution estimates by the Community Multiscale Air Quality (CMAQ-urban) Modeling System. Air pollution exposure was estimated by calculating mean levels of pollutant across each participant’s 3 most commonly visited locations.
Urbanicity scores were derived from 2011 census data; 32% of participants with available data lived in urban settings at age 18.
Analyses controlled for covariates that could confound the data, including the following: family or neighborhood socioeconomic status; maternal or other family history of psychosis; childhood psychotic episodes; smoking or substance abuse; and neighborhood crime or social conditions.
Primary Outcome Measures
The primary outcome measure was the number of psychotic events that occurred between the ages of 12 and 18.
Six hundred twenty-three (30.2%) participants experienced at least 1 psychotic episode, ranging from mild paranoia to severe psychotic symptoms, between ages 12 and 18.
- 1,440 (69.8%) reported no psychotic experiences
- 319 (15.5%) reported 1-2 experiences
- 155 (8%) reported 3-5 experiences
- 138 (6.7%) experienced 6 or more episodes
In terms of air quality, adolescents who had the greatest exposure (top quartile of overall participant exposure) to NO2, NOX, and particulate matter reported more psychotic experiences than those who were consistently exposed to better air quality.
Higher levels of NO2, NOX, PM2.5, and PM10 were significantly associated with urban areas. In fact, mean levels of NOx and PM2.5 in urban areas were found to exceed allowable amounts based on World Health Organization (WHO) guidelines.
Specific pollutants were also looked at for their independent association with adolescent psychoses, and it was determined that the pathways mediating NO2 and NOX accounted for 55% and 58% association, respectively, of urban-dwelling adolescents and psychotic episodes. In combination, NO2 and NOX accounted for 60% of psychotic experiences in urban-dwelling adolescents.
There was no evidence that rates of occurrence were tied to the other potentially confounding factors (eg, socioeconomic status, family history, substance abuse).
The data from this study are important not only for practitioners who are treating adolescents but also those who primarily focus on adult health, given that early psychotic episodes are a risk factor for adult psychoses and warrant early intervention.1 While there is existing data that the prevalence of psychotic episodes is higher among youth brought up in cities,2 and other studies have associated air pollution with a variety of mental health concerns,3,4 few have considered how these 2 variables interact to impact our youth.
As cities become increasingly congested, we are likely to see greater levels of air pollutants from vehicles, industry, and general domestic use of off-gassing products. As a result, practitioners may also encounter more mental illness (not to mention increased cardiac and respiratory concerns5,6) in both adolescents and adults. Many studies suggest that the adolescent brain may be more susceptible to environmental damage.7 For this reason, we should be extending our most comprehensive neurological assessments to our adolescent populations.