Increases in short term exposure to air pollution are associated with higher risk of hospital admissions for depression in urban Chinese populations, according to the results of an article published in the American Journal of Psychiatry in Advance. Prior evidence has suggested that long term exposure to ambient air pollution is linked to the onset of depression.

Xuelin Gu, MBBS, of the department of occupational and environmental health sciences, School of Public Health, Peking University, Beijing, China, and colleagues used data from 2013 to 2017 from the Chinese national medical insurance databases for urban populations. They conducted a 2 stage time series analysis to explore the relationship between short term exposure to major ambient air pollutants and daily hospital admission risk for depression. Pollutants were defined as fine particles (PM2.5), inhalable particles (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO), with data taken from the National Air Quality Monitoring System.

The study identified 111,620 hospital admissions for depression in 75 Chinese cities. Single pollutant models demonstrated significant effect for PM2.5, PM10, NO2, SO2, and CO; however, no significant effect was found for O3. The researchers found that 10 μg/m3 increases in PM2.5, PM10, and NO2 were linked to 0.52%, 0.41%, and 1.78% increases in daily hospital depression admissions, respectively. After controlling for other air pollutants, only the effect estimates of NO2 were significant in sensitivity analyses.

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The researchers suggested that the increased inflammatory response and oxidative stress that accompanies air pollution exposure may affect the central nervous system with both short and long term exposure to these pollutants. They further indicated that short term changes in ambient air pollution may trigger depressive episodes requiring hospitalization among those who suffer from preexisting depression. “Based on our study findings, we suppose that NO2 may be the key air pollutant contributing to the increased depression risk,” the researchers noted.


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Study limitations included ecological bias inherent to time-series analysis method and the lack of specific exposure data for individual subjects. Other factors such as noise, psychological stress, poverty, and population density may also affect the risk of depression. The researchers called for further studies to confirm their findings and investigate the underlying mechanisms involved in this association, as well as analyses in children since younger populations may be particularly susceptible to pollution.

“Targeted strategies such as more stringent air pollution guidelines and air quality control measures may be helpful for promoting public mental health,” the investigators concluded.

Reference

Gu X, Guo T, Si Y, et al. Association between ambient air pollution and daily hospital admissions for depression in 75 Chinese cities. AJP in Advance. 2020. doi:10.1176/appi.ajp.2020.19070748.