Exposure to air pollution could be contributing to a mental health crisis, scientists from Harvard warn.

The researchers, from the college’s T.H. Chan School of Public Health, analyzed emergency department (ED) admission rates for mental health conditions in California during the state’s 2020 wildfires — among the worst in the state’s history before the latest devastation in January.

In particular, they looked at admissions for anxiety, depression, mood disorders and psychosis — or a loss of touch with reality.

Results showed an increase in ED admissions for mental health in areas with higher levels of air pollution from the fires. 

Not only could a life-altering event like a wildfire cause a mental health crisis over fears of losing your home, a loved one or being worried for your livelihood, but researchers believe pollution from the burning is actually damaging the brain. 

Lead researcher behind the study, Dr Kari Nadeau — chair of the Department of Environmental Health at Harvard — said: ‘Wildfire smoke isn’t just a respiratory issue — it affects mental health too.

‘Our study suggests that — in addition to the trauma a wildfire can induce — smoke itself may play a direct role in worsening mental health conditions like depression, anxiety and mood disorders.’ 

Scientists at Harvard University believe the release of pollution from homes burnt in wildfires is causing mental health issues

The above shows the Golden Gate Bridge engulfed in smoke during the 2020 wildfires

Smoke from wildfires has been previously linked to a higher risk of autism and cancer — which scientists said could be caused by breathing in toxins.

Breathing in smoke is also known to raise the risk of multiple other health conditions including heart attacks and lung disease.

In the latest study, the scientists suggested breathing in the smoke was also causing inflammation and damage to the brain — which they said could raise the risk of a mental health episode.

Their study was unable to definitively prove a link, and only suggested an association.

The 2020 wildfires in California were among the worst in the state’s history, with more than 10,000 fires burning destroying 4.2million acres — or about four percent of the states land.

More than 100,000 people were forced to evacuate from their homes amid the blaze while 11,000 buildings were destroyed costing more than $12billion in damage.

A total of 33 people were killed, while more than 1,391 people were hospitalized.

The state has been hit by at least two major wildfire events since – in 2022 and again in Los Angeles early this year.

In the study, published in the journal JAMA Network Open, researchers analyzed data from California from July to December 2020.

For the period, they looked at admissions for people who were admitted to an ED for a mental health condition.

The above shows the distribution of mental health- related emergency department visits by age

The above shows the distribution of mental health- related emergency department visits by race and ethnicity

The above shows the distribution of mental health- related emergency department visits by sex

Mental health conditions patients had included psychoactive substance use disorders, psychotic disorders, mood-affective disorders, depression, and anxiety.

Data was then compared to fine particulate matter, PM2.5, (small particles of pollution in the air) levels by zip code over the same period. 

Overall, they recorded 86,588 mental health admissions over the study period.

The average daily concentration of wildfire-specific PM2.5 was 6.95 micrograms per cubic meter of air initially, but this rose to 11.9μg/m3 during peak wildfire months and 24.9μg/m3 at the highest peak in September.

Average PM2.5 levels in the US are 8.5μg/m3 and the EPA considers anything above 35.5μg/m3 to be unhealthy for sensitive groups and anything above 55.5μg/m3 to be unhealthy for everyone.

Results showed that areas with higher levels of PM2.5 in the air saw a ‘substantial increase’ in admissions for mental health.

A 10 μg/m3 increase in wildfire-specific PM2.5 was linked to a higher number of visits, including for depression, anxiety, and other mood-affective disorders, for up to seven days post-exposure, the researchers found – though they did not specify the exact increase.

People admitted for mental health problems were 38 years old on average and the majority were men. 

Substance use disorder was the leading cause of mental health hospital admissions for adults, men and white people, while anxiety was the leading cause among women, seniors and minors.  

The study also found Hispanic people were most at risk of ED visits for mental health concerns, including for mood affective disorders and depression. 

Additionally, non-mood psychotic disorders were highest among Black individuals – though researchers di not specify which disorders.

Dr Youn Soo Jung, an environmental health expert and lead author on the study, added: ‘The disparities in impact by race, sex, age, and insurance status suggest that existing health inequities may be worsened by wildfire smoke exposure.

‘We need to make sure everyone has access to mental health care during wildfire seasons, particularly the most vulnerable groups and particularly as wildfires become more frequent and severe as a result of climate change.’