New research has found that exposure to air pollution while in the womb is linked to the development of certain mental health issues in adolescence. The University of Bristol-led study, published in JAMA Network Open on May 28, examined the long-term mental health impact of early-life exposure to air and noise pollution.

Growing evidence suggests that air pollution, which includes toxic gases and particulate matter, might contribute to mental health problems. It is believed that pollution could negatively affect mental health through several pathways, such as compromising the blood-brain barrier, promoting neuroinflammation and oxidative stress, and directly entering the brain and damaging tissue.

Despite adolescence being a critical period for the onset of mental health problems, relatively few studies have explored the associations between early-life exposure to air and noise pollution and mental health. This new study aimed to investigate the long-term impact of such exposures during pregnancy, early childhood, and adolescence on three common mental health issues: psychotic experiences (including hallucinations and delusions), depression, and anxiety.

The researchers used data from over 9,000 participants from Bristol’s Children of the 90s birth cohort study (also known as the Avon Longitudinal Study of Parents and Children), which followed the lives of over 14,000 pregnant women from the Bristol area who were recruited between 1991 and 1992.

By linking participants’ early childhood data with their mental health reports at ages 13, 18, and 24, researchers mapped these data against outdoor air and noise pollution levels in South West England at different times. They found that even small increases in fine particulate matter during pregnancy and childhood were associated with more psychotic experiences and depression symptoms in teenage years and early adulthood. These associations persisted after accounting for related risk factors such as family psychiatric history, socioeconomic status, and other area-level factors like population density, deprivation, greenspace, and social fragmentation.

Specifically, the study found that every 0.72 micrograms per cubic meter increase in fine particulate matter (PM2.5) during pregnancy and childhood was associated with an 11% and 9% increased odds of psychotic experiences, respectively, and a 10% increased odds of depression when exposure occurred during pregnancy. Higher noise pollution exposure in childhood and teenage years was linked to more anxiety symptoms.

Dr. Joanne Newbury, Sir Henry Wellcome Postdoctoral Research Fellow in the University’s Bristol Medical School: Population Health Sciences (PHS) and the study’s lead author, emphasized the significance of these findings: “Childhood, adolescence, and early adulthood are critical periods for the development of psychiatric disorders. Our findings add to a growing body of evidence suggesting a detrimental impact of air pollution (and potentially noise pollution) on mental health. This is a major concern, as air pollution is common and rates of mental health problems are increasing globally. Given that pollution is preventable, interventions like low emissions zones could improve mental health, particularly for vulnerable groups like pregnant women and children.”

Dr. Newbury also noted that these findings do not prove a causal association by themselves, but other recent studies have shown positive mental health impacts from low emissions zones.

The research, which included collaborators from King’s College London, University College London, and Cardiff University, was funded by the University of Bristol, Wellcome, the Economic and Social Research Council (ESRC), the Medical Research Council (MRC), the National Institute for Health and Care Research (NIHR), and the Natural Environment Research Council (NERC).

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