Air pollution can quadruple the risk of postnatal depression for up to three years

Previous research has examined air pollution’s impact on postnatal depression however, a team from the USC Keck School of Medicine have taken this further, investigating its impact on depression in the longer term.

Postnatal – or postpartum – depression is one of the most frequent complications associated with childbirth, affecting between 10% to 20% of women worldwide.

361 women from what is known as the MADRES cohort (Maternal and Developmental Risks from Environmental and Social Stressors), were the participants in the study. 

The cohort is made up of over 900 women who were recruited from four community health centers in Los Angeles during pregnancy. The study follows the women and children until the child turns five, monitoring maternal health outcomes including postnatal depression. including asthma, neurodevelopment, and overall health.

Data on mothers’ depressive symptoms one, two and three years after they gave birth was collected and compared to air pollution data near their homes during pregnancy. They found that women exposed to higher levels of NO2 or PM2.5 during the second trimester face an increased risk of postnatal depression more than four times that of women exposed to safer levels. Significantly, they found that this higher risk persists for at least three years after birth.

Specifically, they found that:

• Women with higher levels of exposure to NO₂ during weeks 13 to 29 of pregnancy faced a 3.86 times higher risk of postnatal depression for up to 3 years.
• Women with higher levels of PM₁₀ exposure during weeks 12 to 28 faced a 3.88 times higher risk.
• Overall, 17.8% of women had depressive symptoms after one year, 17.5% after two years and 13.4% after three years.

Tracy Bastain, PhD, an associate professor of clinical population and public health sciences at the Keck School of Medicine of USC and senior author of the study said: ‘What’s really novel about this work is that we were able to extend the examination of depression beyond the first year postpartum, and have shown the sustained effect of air pollution during pregnancy on symptoms of depression all the way through three years postpartum.’

The researchers believe that reducing exposure to air pollution during the second trimester of pregnancy could lower the risk for postnatal depression and they point out that while exercising during pregnancy is important, women should try to avoid exercising outdoors during periods of high pollution, such as morning and evening rush hours or during wildfires.

Bastain added: ‘Another important implication of our work is that depression can persist long beyond the first 12 months postpartum, and mothers should talk to their health care providers if they continue to have symptoms of depression.’