Ozone, a common air pollutant, could be one of the causes behind depressive symptoms in adolescents, according to a new study. The pollutant could have especially profound effects on mental health during the onset of puberty, raising concerns about youth exposure to the chemical. Researchers at the University of Denver and Stanford University found evidence that exposure to ozone in adolescence is linked to depressive symptoms, such as feeling sad or tearful, withdrawing socially, and losing interest or pleasure in activities. The researchers followed the mental health symptoms of 213 adolescents (9 to 13 years old) living in communities with various levels of ozone exposure and determined that those adolescents with higher levels of exposure were more likely to have an increase in depressive symptoms over a four-year period. The study is important as depressive symptoms among youth have become more common in the past two decades, especially among girls. The …