In a new study, researchers examined the relationship between exposure to traffic-related air pollution (TRAP) and symptoms of anxiety and depression mid-childhood. The team, made up of a collaboration between several departments across the Cincinnati Children’s Hospital Medical Center and the University of Cincinnati College of Medicine, was led by Kimberly Yolton.
Their findings indicated that exposure to higher levels of traffic-related air pollution at birth and throughout early childhood corresponded with increased self-reported anxious and depressive symptomology within the population of 12-year-olds studied. Some of the negative side-effects associated with TRAP may be experienced earlier in life than previously known.
This study adds to the growing body of literature on the links between exposure to pollutants (particular contaminants) in childhood and later detrimental cognitive and behavioral outcomes. Air pollution exposure during childhood, operationalized with some variability across studies, has been linked to increased rates of psychiatric drug prescription in childhood, as well as emotional, cognitive, and behavior problems among children.
Prenatal exposure to environmental pollutants has also been linked to increased severity of ADHD-type behaviors and child emotional and behavioral health problems. Though not childhood-specific, correlations have been identified between air pollution levels and suicide rates.
The World Health Organization (WHO) recently recognized air pollution as “the world’s largest single environmental health risk.” Given the increasing prevalence of a spectrum of mental health disorder classifications, and anxiety and depression among adolescents in particular (estimated in Yolton and colleagues’ publication at 30% and 14%, respectively), air quality may be an important component of a complex equation for risk in the context of urbanization.
“While genetics, family history, socioeconomic status, and medical conditions play an important role in mental health disorders, environmental factors may also influence their development through oxidative stress and neuroinflammatory pathway,” the researchers write.
“Accumulating epidemiologic evidence supports the neurotoxic effects of air pollution with studies reporting associated cognitive deficits and externalizing behaviors in children, and accelerated cognitive decline in adults.”
Yolton and team used data from the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), birth records from the Ohio and Kentucky Departments of Health, and clinical evaluations at ages 1, 2, 3, 4, 7, and 12 to examine anxiety and depression levels among participants (n = 344) at 12-years-of-age. Parent ratings of child symptomology were gathered using the Behavior Assessment System for Children-2, and child ratings were reflected in scores from the Child Depression Inventory-2 (CDI-2) and the Spence Children’s Anxiety Scale (SCAS). Levels of TRAP at various time points (birth, 12 years, and average exposure throughout childhood) were evaluated based on elemental carbon attributable to traffic (ECAT) according to a land-use regression model.
The researchers found that traffic-related air pollution (TRAP) exposure was “associated with increased self-reported symptoms of depression and anxiety at age 12 years.” Additionally, they observed “exposures occurring during early childhood to have the greatest association with depression at age 12.”
“Similarly, exposure to TRAP during early childhood was the only period significantly associated with total anxiety, though nonsignificant trends were evident for TRAP exposure at age 12, as well as average childhood exposure, with total anxiety scores. Notably, increased generalized anxiety was consistently associated with TRAP exposure at all childhood time periods, and for social phobia, associations were positive and significant for current and average childhood exposure.”
Parent reports of childhood anxiety and depression were not found to be significantly associated with TRAP at birth, in later childhood, or overall. However, self-reported childhood anxiety and depression ratings were significantly higher at birth, and various types of anxiety (e.g., generalized anxiety and social phobia) were associated with specific symptoms of anxiety across multiple time points and on average.
Additional research is needed to obtain a clearer picture of features of risk across various populations, but overall, results from this study contribute to the “growing body of epidemiologic evidence for the role of air pollution in neurobehavioral and mental health disorders.”
Yolton, K., Khoury, J. C., Burkle, J., Lemasters, G., Cecil, K., & Ryan, P. (2019). Lifetime exposure to traffic-related air pollution and symptoms of depression and anxiety at age 12 years. Environmental Research, 173, 199-206. (Link)