Secondhand smoke exposure may raise a child’s risk for depression symptoms
Secondhand smoke (SHS) has been tied to a number of health risks in children, such as respiratory problems, ear infections, and even later development of heart disease and lung cancer. However, little research has been conducted into how secondhand smoke may affect the mental health of a developing body.
Now, a new study published in the journal Nicotine and Tobacco Research shows that secondhand smoke can significantly increase a child’s chances of developing depression.
According to the study including more than 1,500 Canadian elementary school students, exposure to SHS at both home and in cars was directly related to significantly higher scores on the Depressive Symptoms Scale.
The findings show that SHS exposure during 5th grade baseline testing was linked to higher rates of depressive symptoms during 6th grade, as well as during the period between 6th and 7th grade. However, this statistical link essential disappeared after two years.
As the researchers explain, any form of exposure “at any age did not predict depressive symptoms two years later.”
“Because this was a prospective study, we were able to follow this group over multiple years,” coinvestigator Karen M. Wilson, MD, professor and division chief of general pediatrics and vice-chair for clinical and translational research, Icahn School of Medicine at Mount Sinai and Kravis Children’s Hospital, New York City, told Medscape Medical News.
“We found a significant relationship between overall exposure and development of depression, as well as a relationship between exposure at time 1 and depression 1 year later. Although it was interesting that that did not hold up into the second year, there are some possible explanations for that,” she said.
The findings are particularly important in light of the high risk for young people to be exposed to secondhand smoke. In one 2015 Canadian assessment, researchers found that up to 80% of young people between the ages of 12 and 19 were exposed to at least some amount of secondhand smoke in the past month.
While American statistics indicate significantly lower rates of secondhand smoke exposure, the CDC still estimates at least 58 million nonsmokers are exposed to SHS every year in the U.S.
“People often think secondhand smoke is something that affects younger children, particularly with respiratory illnesses like asthma. We know from other studies that [SHS] can be associated with other problems as well, including mental illness and psychiatric conditions,” said Wilson.
“So we were really interested to look at whether there was an association between secondhand smoke exposure and development of depression in teenagers,” she added.
For the latest study, the team evaluated data collected from 1553 participants who had never smoked as part of the AdoQuest1 study. Starting in 2005, the researchers followed the participants in five waves.
The first wave was baseline testing during 5th grade, followed by a second wave during 6th grade. The third wave included 7th grade students, while the fourth wave included 9th grade and the fifth wave covered 11th grade.
Notably, more than 400 of the participants began smoking during the course of the study.
According to the findings, exposure to SHS smoke significantly increased the rate of depression symptoms for up to two-years after a person’s exposure. However, this link evaporated by the two-year mark.
Still, the researchers say that “SHS has deleterious effects on physical health and results of this study raise concerns that such exposure might also affect the mental health of young persons.”
The study had a few important caveats. Firstly, the study did not include young adults who began smoking before the start of the study, preventing a comparison between depression rates from direct exposure to cigarette smoke and secondhand smoke exposure. Secondly, the researchers did not assess whether parents of participants had depression, limiting the ability to discern between hereditary risk for depression and the risk of depression symptoms after SHS exposure.