We all know that smoking is bad for you, and smoking in pregnant women can be especially dangerous as it affects the health of their children. However, although past research has suggested a link between tobacco use in mothers and mental illness in offspring, a new study has found that most of the association is likely to be explained by family risk and not the mother’s smoking habit.

A study now published online in JAMA Psychiatry has found little evidence to suggest smoking during pregnancy directly causes a higher risk of bipolar disorder, schizophrenia, and other serious mental health conditions in their offspring. Although children exposed to moderate and high levels of smoking during pregnancy had greater severe mental illness rates than their counterparts, when familiar factors were taken into consideration, this association was no longer significant.

Read: Smoking During Pregnancy Could Increase Risk Of Your Children Having Schizophrenia

“The study didn't prove that smoking caused severe mental illness in offspring,” the researchers said in a recent press release. “Rather, these results suggest that much of the observed population-level association can be explained by measured and unmeasured factors shared by siblings.”

For the study, the team of researchers, led by by Patrick D. Quinn, Ph.D., of Indiana University, Bloomington, analyzed data for nearly 1.7 million people born in Sweden to understand the differences between children born to mothers who smoked during pregnancy and those born to mothers who did not not smoke. While results suggested that maternal smoking during pregnancy did raise the risk of mental health conditions in offspring later on in life, the team admitted that it may be too early to conclude that one action without a doubt led to the other.

This research addresses past studies which suggested a link between  schizophrenia and other mental health illnesses and maternal smoking during pregnancy. In 2016, researchers from Columbia University Medical Center found that smoking during pregnancy causes changes to the fetus' DNA that lead to mental health issues later in life such as increased risk of schizophrenia.

“To our knowledge, this is the first biomarker-based study to show a relationship between fetal nicotine exposure and schizophrenia,” said Dr. Alan Brown, senior author and Mailman School professor of epidemiology and professor of clinical psychiatry at CUMC, in a press release. “We employed a nationwide sample with the highest number of schizophrenia cases to date in a study of this type.”

While the most recent study may have not found a direct link between maternal smoking and offspring mental health, that’s not to say the habit does not have a number of health consequences. For example, earlier this year a study found that smoking contributed to one in 10 deaths around the world, with around half of these smoking related deaths occurring in China, India, Russia, and the U.S. So, regardless of its disputed effect on fetal health, smoking is a habit best to be kicked.

Source: Quinn PD, Rickert ME, Weibull CE, et al. Association Between Maternal Smoking During Pregnancy and Severe Mental Illness in Offspring. The JAMA Network. 2017

See Also:

Maternal Grandmother's Smoking During Pregnancy May Increase Autism Risk In Grandchildren

Smoking Risks 2016: How Nicotine Affects The Body

Correction: This article has been updated to correctly represent the findings of this study. It now states that the link between maternal smoking and offspring’s chances of developing a mental health disease is inconclusive.