Wildfire smoke drives a surge in mental health crisis

The thick, irritating smoke that covered California during the record 2020 wildfire season has significantly increased emergency room visits for depression, anxiety and other mental health conditions, according to a groundbreaking study published on the Jama Network, which opens this week.

Scientists analyzing visits from more than 86,000 emergency departments found that for every slight increase in wildfire smoke pollution, mental health emergency increased by up to 29% the following day, with children, women and racial minorities experiencing the most severe effects.

“These findings suggest a potential link between wildfire-specific PM2.5 exposure and mental health outcomes,” the researchers concluded, adding, “healthcare professionals and systems should prepare for the potential for an increased demand for mental health-related emergency services during wildfire events.”

The study, led by researchers at Harvard and Stanford University, provides the most comprehensive evidence to date that directly links the most comprehensive evidence to the mental health crisis, beyond the obvious trauma of evacuation, loss of property, or physical injury.

During the peak wildfire month of 2020, Californians were exposed to a median daily concentration of 11.9 micrograms of wildfire-specific particulate matter (PM2.5) per cubic meter. For context, the EPA considers more than 35 micrograms that are unhealthy for sensitive groups.

For every 10 mirograms of this wildfire-specific contamination increased, the researchers recorded an 8% increase in all mental health emergency visits, a 15% increase in depression-related visits, and an astonishing 29% jump in other mood disorders the following week.

Perhaps the most concern is the disparity in who suffered the most. Women were at a 17% higher risk of emergency visits of depression within four days of exposure compared to men. Young people showed an increase in emergency visits for mood disorders by 46%, while blacks showed an extraordinary 135% risk for similar conditions within five days of smoke exposure.

Hispanic individuals were also unavoidable, and the risk of depression-related emergency visits up to one week after smoke exposure increased by 30%.

“A growing range of studies suggests that exposure to particulate matter may be related to mental health outcomes,” the researchers noted when explaining the importance of the study. “However, the potential impact of wildfire-specific PM2.5 exposure on mental health remains known.”

These findings are particularly important considering the unprecedented fire season of 2020, when over 70% of California’s population withstanded unhealthy air quality for more than 100 days. The state experienced 98 major wildfires, each burning over 1,000 acres. The largest consumption exceeds 1 million acres, with some flames still lasting for 140 days.

Previous studies have established a link between general air pollution and mental health, but this study suggests that wildfire smoke may be even more harmful. Researchers point to the unique composition of wildfire smoke particles. This is more toxic than typical urban air pollution.

When inhaled, these microscopic particles (more than a single human hair) can reach the brain, potentially causing neuroinflammation, oxidative stress, and cerebral vascular damage. These biological mechanisms may explain why exposure correlates with an increase in mental health emergency.

The timing of mental health effects varies depending on the conditions. Depression and mood disorders showed an increase in emergency visits throughout the week after exposure, while anxiety-related visits spiked about 3 days after smoke exposure.

Particularly troublesome is the discovery that children and young people appear particularly vulnerable. Young people showed a 17.4% higher risk of mental health emergency per unit of smoke exposure, further increasing in certain conditions such as depression and mood disorders.

The authors of this study point out that this increased risk may be attributed to developmental factors. “Childhood and adolescence and key periods of brain development are particularly vulnerable to wildfire smoke toxicity, which can increase the risk of mental disorders.”

Insurance situation also appeared to have an impact on vulnerability. Medicaid recipients usually earn less – the risk of emergency mental health visits increased significantly, but the risk of private insurance did not show a statistically significant increase. This suggests that socioeconomic factors can exacerbate the mental health risks of wildfire smoke exposure.

To rule out the possibility that smoke might promote these increases rather than smoke, researchers compared areas with or without evacuation orders and found similar patterns in both. This reinforces cases where smoking itself has a direct effect on mental health, rather than displacement or property damage.

As climate change continues to intensify wildfire seasons across the West of the United States and around the world, these findings suggest that the mental health burden of these disasters may be much greater than previously recognized. This study highlights the importance of considering the impact of mental health in disaster planning and response, particularly for vulnerable populations.

With California and other western states already experiencing another active fire season in 2025, among the populations identified as the most vulnerable, they may need to prepare for an increase in demand for mental health services within days and weeks of smoke exposure.

This study serves as a clear reminder that the effects of climate-driven disasters go far beyond the obvious physical dangers and that even after the flames have disappeared, they affect human health in complex and sometimes invisible ways.