High pollen count: The last straw effect on suicide risk

"A small shock could have a big effect if you're already in a vulnerable state," said Joelle Abramowitz, associate research scientist at U-M's Institute for Social Research. "We looked specifically at pollen from all different kinds of plants, including trees, weeds and grasses."

The effect is incremental. Researchers divided pollen levels into four tiers and found the suicide risk rose with each group: it increased by 4.5% in the second level, 5.5% in the third and peaked at 7.4% in the fourth and highest category.

The study, funded by the American Foundation for Suicide Prevention and U-M ISR, combines daily pollen data from 186 counties of 34 metropolitan areas across the United States, with suicide data from the National Violent Death Reporting System between 2006 and 2018.

Abramowitz and co-authors Shooshan Danagoulian and Owen Fleming of Wayne State University said that while structural factors for suicide are well-researched, short-term triggers are less understood. Pollen allergies are an ideal subject for this research, considering they are an exogenous shock-meaning they are external and not caused by an individual's mental health status.

"During our study period, there were nearly 500,000 suicides in the U.S.," Abramowitz said. "Based on our incremental data, we estimate that pollen may have been a contributing factor in up to 12,000 of those deaths over the period, or roughly 900 to 1,200 deaths per year."

Vulnerable populations

Published in the Journal of Health Economics, the study also found that individuals with a known mental health condition or who had received prior mental health treatment had an 8.6% higher incidence of suicide on days with the highest pollen levels. White men strongly drive the effect, but the study also found an unexpectedly high vulnerability among Black individuals.

"While our study's data comes from the U.S., our findings likely apply globally," Abramowitz said. "This is supported by earlier research that found similar relationships in locations like Tokyo and Denmark. Our results, therefore, provide crucial new evidence that this phenomenon is a consistent, worldwide trend."

Public health and awareness

The focus should be on public health and education, as reducing the number of pollen-producing plants isn't a viable option, the researchers suggest. This includes more accurate pollen forecasting and better public communication. Providing people with clear, timely information about high-pollen days allows them to take proactive steps. Additional recommendations are limiting outdoor activities, wearing a mask or having antihistamines on hand.

There is also a need for a broader approach to mental health awareness, the authors said. Health care providers, particularly those in primary care, can benefit from understanding the connection between environmental factors, such as pollen, and patient well-being. This knowledge could help them tailor care more effectively, especially for vulnerable patients, and serve as a prompt to discuss mental health and stress management during high-pollen seasons or other periods of environmental stress.

"We should be more conscious of our responsiveness to small environmental changes, such as pollen, and our mental health in general," Abramowitz said. "Given our findings, I believe medical providers should be aware of a patient's allergy history, as other research has also established a connection between allergies and a higher risk for suicide. I hope this research can lead to more tailored care and, ultimately, save lives."

The authors predict that as climate change extends and intensifies the pollen season, the impact of allergies on suicide rates could more than double by the end of the century.

Reference:

Joelle Abramowitz, Shooshan Danagoulian, Owen Fleming, Seasonal allergies and mental health: Do small health shocks affect suicidality?, Journal of Health Economics, https://doi.org/10.1016/j.jhealeco.2025.103069