Smoke from wildfires does more than damage lungs—it may also take a toll on mental health. A new study led by researchers at the Harvard T.H. Chan School of Public Health has found that exposure to fine particulate matter (PM2.5) from wildfire smoke is associated with increased emergency department (ED) visits for mental health conditions across California.
The findings, published in JAMA Network Open, add to growing evidence that air pollution affects not only the body but also the mind. The research team, led by Dr. Kari Nadeau, chair of the Department of Environmental Health at Harvard, says this is the first study to focus specifically on the short-term mental health impacts of PM2.5 pollution from wildfires.
“Wildfire smoke isn’t just a respiratory issue—it affects mental health, too,” said Dr. Nadeau. “Smoke itself may directly worsen conditions like depression, anxiety, and mood disorders, beyond the emotional trauma that often comes with living through a wildfire.”
Fine particulate matter, or PM2.5, consists of tiny particles less than 2.5 micrometers in diameter—small enough to be inhaled deep into the lungs and even enter the bloodstream. While its harmful effects on the heart and lungs are well-documented, its influence on mental health is still being explored.
To better understand this connection, the researchers studied health data across California from July to December 2020, the most severe wildfire season in the state’s history. During that time, 86,588 visits to emergency departments were recorded for mental health issues, including depression, anxiety, substance use disorders, and psychotic episodes.
The study mapped these visits alongside daily wildfire-specific PM2.5 levels, which were measured at the zip-code level. On average, the daily concentration of PM2.5 was 6.95 micrograms per cubic meter of air (μg/m³), but it spiked to 11.9 μg/m³ during peak wildfire months and reached as high as 24.9 μg/m³ in September.
The researchers found a clear pattern: when wildfire-related PM2.5 levels rose by just 10 μg/m³, emergency visits for mental health conditions also increased. This effect was observed not only on the day of exposure but continued for up to seven days afterward.
The impact wasn’t equal across all groups. Women, children and young adults, Black and Hispanic individuals, and people enrolled in Medicaid were the most affected. These findings highlight how wildfire smoke may worsen existing social and health inequalities.
“The disparities in impact by race, sex, age, and insurance status suggest that existing health inequities may be worsened by wildfire smoke exposure,” said lead author YounSoo Jung. “We need to make sure everyone has access to mental health care during wildfire seasons—especially vulnerable groups—as wildfires become more frequent and severe due to climate change.”
Review and Analysis
This study is a major step forward in understanding how air pollution from wildfires affects mental health in the short term. Most previous research has focused on how wildfire smoke impacts breathing or heart problems. But this new study shows that mental health emergencies—especially for mood and anxiety disorders—also increase after smoke exposure.
One of the key strengths of the study is its scale. It analyzed data from across the entire state of California during a period of extreme wildfire activity, using daily air quality readings at the local level. This helped the researchers make precise connections between pollution levels and health outcomes.
The findings are also important for public health planning. As wildfires become more common with climate change, communities will need stronger systems to support mental health during and after smoke events.
That might include making counseling more accessible, sending out mental health alerts during smoke waves, and preparing hospitals for potential surges in psychiatric care.
The study also draws attention to social inequalities. People who already face barriers to care—such as low-income individuals, racial minorities, and young people—are more vulnerable to the harmful mental health effects of wildfire smoke. Addressing these gaps is essential to ensure fair access to treatment and support.
In summary, wildfire smoke is not just a physical hazard—it is also a mental health risk. This research calls for a broader response to wildfire seasons that includes not only masks and air purifiers, but also mental health services tailored to reach those most in need.
If you care about mental health, please read studies about 6 foods you can eat to improve mental health, and B vitamins could help prevent depression and anxiety.
For more health information, please see recent studies about how dairy foods may influence depression risk, and results showing Omega-3 fats may help reduce depression.
The research findings can be found in JAMA Network Open.
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