Air Pollution Linked to Adolescent Psychotic Experiences

Higher exposure to air pollutants, especially NO2 and NOx, was found to be associated with greater odds of psychotic experiences in adolescents.

Joanne B. Newbury, PhD

A long-term population-based cohort study of children born in the UK found that exposure to air pollution was associated with increased the odds of psychotic experiences for adolescents.

Investigators Joanne B. Newbury, PhD, Louise Arseneault, PhD, Sean Beevers, PhD, and colleagues said that this exposure could partly explain the association between living in an urban setting and psychotic experiences in adolescents.

“Given that 70% of the world’s population will be urban by 2050, uncovering the mechanisms linking the urban environment to psychosis and developing preventive interventions constitute an urgent health priority,” wrote Newbury, et al.

In an accompanying editorial, Marianthi-Anna Kioumourtzoglou, ScD, highlighted the importance of research investigating the factors of urban life that influence mental health.

“Identifying those urban environmental exposures that ameliorate or worsen mental health can inform regulatory action, development of targeted interventions, and the (re-)design of neighborhoods, communities, and cities with the goal of prevention of mental health disorders and promotion of well-being through urban planning,” wrote Kioumourtzoglou.

Marianthi-Anna Kioumourtzoglou, ScD

The study pulled data from the Environmental-Risk Longitudinal Twin Study that included 2232 children born in England and Wales from January 1, 1994, through December 4, 1995. Children were followed up with from birth to 18 years of age, when they provided data on psychotic experiences.

Investigators modeled the pollution exposure for participants when they were 17 years old at their home addresses and 2 additional locations (school, work, shops, etc) where each participant reported spending their time. Urbanicity on a 3-point scale was estimated using census data from 2011.

The study found that 623 participants (30.2%) had at least 1 psychotic experience during adolescence (12 to 18 years of age). Psychotic experiences were significantly more common among participants with the highest levels of exposure to air pollutants: NO2 (odds ratio [OR], 1.71; 95% CI, 1.28-2.28), NOx (OR, 1.72; 95% CI, 1.30-2.29), and PM2.5 (OR, 1.45; 95% CI, 1.11-1.90). These odds ratios were adjusted for family-level factors, childhood psychotic symptoms, adolescent substance use, and neighborhood factors like socioeconomic status, crime, and social conditions.

When adjusting for variables, there was not an association between levels of PM10 and adolescent psychotic experiences.

The investigators suggested several possible mechanisms to explain the association the results showed. They mentioned the oxidative effects air pollution has on lipids and proteins, which could contribute to the disruption of the nasal epithelium and blood-brain barrier.

They also noted that exposure to air pollution has been linked to lower serum vitamin D levels, which itself has been linked to childhood psychotic episodes.

Finally, since NO2 and NOx are closely tied to vehicle emissions, the authors point out the link to road traffic and therefore noise pollution. They suggested that the observed association in their study may have been due to road traffic and noise pollution.

The authors noted that while their study has limitations, the results have research, clinical, and public health implications. On the public health aspect, they noted that NO2 levels below the European Union threshold were still found to be significantly associated with adolescent psychotic experiences, and thus, those thresholds may be too “lax.”

In her editorial, Kioumourtzoglou also commented on the public health implications.

“Although air pollution exposures are ubiquitous in urban environments, they are modifiable and can be reduced through rigorous regulatory action,” wrote Kioumourtzoglou. “Unfortunately, regulatory action does not always follow scientific evidence.” She added that in this situation other factors—such as lifestyle, nutritional, or neighborhood-level factors—are especially important to identify and leverage.

The study, “Association of Air Pollution Exposure With Psychotic Experiences During Adolescence,” and editorial, “Identifying Modifiable Risk Factors of Mental Health Disorders—The Importance of Urban Environmental Exposures,” were published in JAMA Psychiatry.