Prenatal air pollution linked to mental health problems in teens

A study conducted by the University of Bristol and published in JAMA Network Open found that fetal exposure to air pollution is associated with the development of certain mental disorders in adolescence.

Growing evidence suggests that air pollution, including toxic gases and particulate matter, may contribute to mental health problems. Pollution is thought to have a number of negative impacts on mental health, including disrupting the blood-brain barrier, promoting neuroinflammation and oxidative stress, and directly penetrating the brain and damaging tissue.

Despite adolescence being a key period for the onset of these problems, relatively few studies have so far examined the links between early life exposure to air pollution and noise and mental health.

In the new study, the researchers aimed to examine the long-term effects of exposure to air pollution and noise during pregnancy, early childhood and adolescence on three common mental health problems: psychotic experiences (including hallucinations and delusions), depression and anxiety.

To do this, the team used data from more than 9,000 participants in the Children of the 90s study (also known as the Avon Longitudinal Study of Parents and Children), which recruited more than 14,000 pregnant women in the Bristol area between 1991 and 1992 and has been following the women, their children and partners ever since.

By matching the participants' early childhood data with their mental health reports at ages 13, 18 and 24, the researchers were able to use the data to create a map of outdoor air pollution and noise in south-west England at different time points.

The researchers found that relatively small increases in fine particulate matter (PM2.5) during pregnancy and childhood were associated with more psychotic experiences and depressive symptoms in adolescence and early adulthood. These associations persisted after accounting for many associated risk factors, such as family psychiatric history, socioeconomic status, and other neighbourhood-level factors such as population density, deprivation, green space, and social fragmentation.

The team found that each 0.72 micrograms per cubic metre increase in PM2.5 concentration during pregnancy and childhood was associated with an 11 per cent increase in the odds of psychotic experiences and a 9 per cent increase in the odds of depression. In contrast, higher exposure to noise pollution during childhood and adolescence was associated with more anxiety symptoms.

Childhood, adolescence, and early adulthood are critical periods for the development of mental disorders, with nearly two-thirds of those affected globally developing the condition by age 25. Our findings add to a growing body of evidence showing the detrimental impact of air pollution (and potentially noise pollution) on mental health.

This is a major concern as air pollution is a very common exposure and levels of mental health problems are rising around the world. Given that pollution is a preventable exposure, exposure reduction measures such as low emission zones can potentially improve mental health. Targeting vulnerable groups, including pregnant women and children, can also reduce exposure more quickly.

It is important to emphasize that these findings do not, in and of themselves, prove cause and effect. However, other recent studies have shown that low-emission areas seem to have a positive effect on mental health.