Air Pollution Affects Depressive Symptoms in Bipolar Disorder

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Recent research assessed the association between localized mean air quality index and the symptom severity of depression and mania in individuals with bipolar disorder, and found worsened air quality increased symptoms of depression.

“This is the first study to find that real-time air pollution exposure is associated with acutely increased depression symptoms in people with bipolar disorder,” wrote the study authors.¹

By using a digital health care platform called juli, which reports air pollutant levels to users as the daily air quality index (AQI),² researchers were able to examine the cross-sectional association between 2-week mean AQI and symptoms of depression and mania. Researchers examined 1423 participants with bipolar disorder who completed PHQ-8 and ASRM questionnaires. Of this group, 1142 (80.3%) were female, 701 (49.3%) had received a diagnosis for more than 5 years, and 723 (50.8%) continue to see a psychiatrist regularly. The AQI ranged from 2 to 235 (mean 43, standard deviation 23). The PHQ-8 scores ranged from 0 to 24 (mean 12.8, standard deviation 5.9) and the ASRM scores ranged from 0 to 20 (mean 4.75, standard deviation 3.9).

“We examined how the mean AQI over these 2 weeks was associated with the total score on the PHQ-8 and ASRM in individuals with bipolar disorder using linear regression,” said the study’s authors.¹

Researchers adjusted for potential confounders of the relationship between AQI and PHQ-8/ASRM, including the user’s age and gender, mean daily step count, mean temperature, and mean humidity over the 14 days. Depression symptoms were measured using the Patient Health Questionnaire-8 (PHQ-8), and mania symptoms were measured using the Altman Self-Rating Mania scale (ASRM). The AQI ranges from 0-500, with higher scores reflecting worse pollution; AQI values at or below 100 are satisfactory and values over 100 are unhealthy.²

According to previous studies, air pollutants such as particulate matter, nitrogen dioxide, sulfur dioxide, ozone, and carbon monoxide, are associated with unipolar depression in both the long- and short-term.³

“Air pollutants potentially play a role in mental health problems through inducing neurotoxicity, neuroinflammation and hormonal dysregulation,” said the study authors.¹ “Therefore, air pollution may represent an important modifiable risk factor for symptom severity in various mental health problems, including bipolar disorder.”

References

1. Kandola A, Hayes JF. Real-time air pollution and bipolar disorder symptoms: a remote monitored cross-sectional study. medRxiv. 2022;22282067.

2. Fitz-Simons T. Guideline for reporting of daily air quality: Air Quality Index (AQI). Environmental Protection Agency, Office of Air Quality Planning and Standards. 1999. Accessed December 13, 2022. https://www.osti.gov/biblio/698786

3. Borroni E, Pesatori AC, Bollati V, et al. Air pollution exposure and depression: a comprehensive updated systematic review and meta-analysis. Environ Pollut. 2022;292(Pt A):118245.