Extreme heat tied to postpartum depression in Southern California

Exposure to extreme heat has been shown to impact mental health in previous epidemiological studies, but there are a very limited number of studies that investigate the relationship between high-temperature exposure and mental health among pregnant women and no past study explored its impact on postpartum maternal mental health.

To address this knowledge gap, a study recently published in the journal Environmental Health Perspectives led by Jun Wu, Ph.D., professor of environmental & occupational health at UC Irvine Joe C. Wen School of Population & Public Health, and team found that a cohort of mothers in Southern California that were exposed to higher temperature during the postpartum period was associated with an increased risk for postpartum depression (PPD).

“Our finding builds upon our team’s previous work connecting long-term exposure to air pollution and the increased risk for PPD,” says Wu. “Air pollution and heat make a harmful combination on our bodies as rising temps can stimulate our body to absorb more air pollution through sweat, increased skin blood flow, and breathing more.”

The team conducted a retrospective cohort study of data from over 430,000 women in the Kaiser Permanente Southern California electronic health records who had live singleton births at KPSC facilities between Jan. 1, 2008, and Dec. 31, 2018. The health data was paired with historical daily ambient temperature data that included the amount of air pollution (fine particulate matter and ozone), exposure to green space within 500 meters, and access to air conditioning.

“We found that temperature related PPD risks were greater among African American, Asian, and Hispanic mothers compared with their counterparts,” shares Yi Sun, Ph.D., the first author of the study.

“Higher temperature also showed a stronger association with PPD among mothers who had higher air pollution exposure, lower greenspace levels, and lower access to air conditioning.”

Wu’s previous work has shown that exposure to green space was associated with a reduced risk of PPD. Additional targeted interventions are needed for mothers, especially those of marginalized communities, exposed to higher temperatures and temperature ranges and living in regions with higher air pollution, lower green space levels, and less access to AC across the State of California.