Jai Dhar looks through the window of his New Delhi house and sees the thick smog that has engulfed the city. With his severe allergies and asthma, the pollution makes it difficult for him to breathe. It also leaves him feeling gloomy.

"The whole city has suddenly changed. It looks like a ghost city," the 52-year-old said.

When temperatures started to drop in mid-November, the air quality index (AQI) in India's capital city moved into the severe category. According to the World Health Organization, an AQI above 300 is considered hazardous. In the two weeks starting Nov. 13, New Delhi's average AQI was 492.

Ranked as one of the most polluted cities in the world, New Delhi's 20 million residents have experienced increases in respiratory illnesses and other issues like allergic rhinitis, headaches and skin issues. 

Now the effect of air pollution on mental health is also emerging as a cause for concern, experts say.

Describing himself as a "victim of air pollution," Dhar said he constantly has to use a nebulizer — a small machine that delivers medicine in a mist — which triggers his health anxiety and affects his day-to-day life. 

Winter, with its worsening air quality, leaves him feeling depressed and helpless and he doesn't even enjoy the Hindu festival of Diwali anymore. The celebration often takes place just before temperatures drop and the bursting of firecrackers contributes to the deteriorating air quality.

"The air pollution makes everything worse."

Physical, mental health treated at new clinic  

At the city's Ram Manohar Lohia Hospital, a pollution clinic — the first of its kind in Delhi — opened in October 2023. In addition to doctors dealing with respiratory, skin and eye issues, the clinic also has psychiatrists, a decision sparked by growing evidence linking air pollution on mental health.

"The idea was to bring all the concerned specialists, including mental health, under one roof and make it easy for patients to seek help," said Dr. Amit Suri, head of the clinic. 

On Dec. 5, Delhi was allowed to relax the strict emergency restrictions put in place on Nov. 18 to tackle rising air pollution. Some of the Graded Response Action Plan (GRAP) Stage 4 measures included shutting schools and colleges and halting non-essential construction.

The clinic's senior resident psychiatrist, Priyanka, who goes by her first name only, says mental health issues mostly affect children and elderly people but said all ages can experience changes to mental well-being as a result of their physiological reactions to pollution.

Fine particulate matter in the air, often called PM2.5, can cross the blood-brain barrier causing inflammation, and changing the brain's chemical reaction, she said. PM2.5 refers to particulate matter less than 2.5 microns in diameter. The width of a human hair is around 75 microns.

In children, pollution has been linked to impaired neurodevelopmental growth, impacting abilities like memory, learning and speaking. They can be left feeling dizzy and sad and might experience difficulties coping with their studies, she said. 

In the elderly, pollution affects their cognitive decline, which results in forgetting and loneliness, she said. 

Priyanka said there is a lack of awareness about mental health issues in India, as well as a social stigma that prevents people from seeking professional help.

"The people who are already facing mental health issues are more vulnerable to pollution," she added. "It can exacerbate their stress and anxiety and can lead to depression." 

New research

Uttara Balakrishnan is a senior research economist at the Virginia-based American Institute for Research whose work often looks at specific situations in developing countries.

In 2021, Balakrishnan was lead author of a study about the mental health impact of air pollution in India. It found that air pollution exposure in a specific calendar year saw significantly worsened mental health in the following year.

"It was an understudied topic, and we wanted to fill in the causal link, not just correlation, between air pollution and mental health," said Balakrishnan, who did part of her schooling at the University of Delhi.

Balakrishnan said the team's approach looked at variables that can affect air pollution exposure, like where people live, their working conditions, and their physical health. 

"Mental health is also correlated with poverty and income," she said. "Any developing country — like India, Pakistan, and Bangladesh — would have high levels of mental health issues because poor mental health results in lower labour force participation and higher health-care utilization and could perpetuate poverty." 

In 2023, Cambridge University Press published a review that assessed existing research on air pollution and mental health, and suggested some priorities for future studies.

"When it comes to the correlation between mental health and air pollution, the scope of such studies is limited," said Dr. Pallavi Rajhans, a Delhi-based psychiatrist who was not part of the review. "With air pollution becoming a major concern, more research should be conducted in this area."

Mental health concerns were also identified in a Delhi government report about air pollution that was submitted in April to the National Green Tribunal, India's environmental court. According to news reports, the government advised measures like being active or talking to a therapist to combat feelings of sadness, cognitive difficulties and a reduced ability to cope with life's challenges.

'I don't know what the future looks like'

Aparna Aggarwal is dismayed about the state of affairs in the city. 

For weeks, her two children, six-year-old Avni, and Avir, 4, had difficulty breathing and needed to use the nebulizer every day. They've been irritable with aggressive behaviour and mood swings.

She feels "helpless and agitated."

Before schools were closed down in mid-November by GRAP 4 restrictions, her son's teacher told her Avir had complained of being sad and unhappy but didn't know why.

Deteriorating air quality meant they couldn't go outside on the balcony or to the park, she said. "They have been complaining of constant headaches. Most of the time they are inside, and they feel constrained."

After weeks of virtual classes, missing their friends and limited outdoor activity, the air quality has improved and many restrictions have lifted. But it's "a temporary relief," Aggarwal  said. 

"Seeing this air pollution slowly killing my children, I don't know what the future looks like."