(NewsNation) — A new study indicates that long-term exposure to air pollutants could directly correlate to an increased risk for depression.

The study published in Environmental Science and Ecotechnology and conducted by Harbin Medical University and Cranfield University examined the link to depressive symptoms in a 45-year-old and over Chinese adult population and six common air pollutants over 7 years.

Sulfur dioxide (SO₂) was the primary pollutant linked to an increased risk of depression, and carbon monoxide (CO) and fine particular matter

The findings point to sulfur dioxide as the most influential pollutant associated with increased depression risk. Particulate matter (PM2.5) and carbon monoxide also contributed to a heightened risk for mental health illness, according to the research. When an individual is exposed to a combination of pollutants, the possibility for depression is heightened.

According to the authors of the study, “Essentially, air pollutants could affect the central nervous system through oxidative stress and inflammatory responses, potentially via systemic circulation, the trigeminal nerve, or olfactory receptor neurons. Further investigation is necessary to elucidate the precise processes that link air pollution exposure to mental health outcomes.”

Depression is a mood disorder that causes consistent feelings of sadness and loss of interest. It is also referred to as clinical depression. Symptoms of depression could be anxiety, sleeplessness, fatigue, irritability, loss of pleasure in activities, among others, according to the Mayo Clinic.

If an individual should experience any symptoms of depression that should consult a medical professional.