Scientists already know that smoking during pregnancy changes a fetus’ DNA, which then harbors the negative health effects that the child will be born with, including low birth weight and mental health issues later on. Now, a new study points to a potentially devastating repercussion of pregnant smoking: an increased risk of schizophrenia in the mothers' children.

The study, published in the American Journal of Psychiatry, discovered that higher maternal nicotine levels in a mother’s blood was linked to a higher risk of schizophrenia among their children. The results — possibly the first to find such a strong link between the two — highlight the importance of avoiding smoking during pregnancy. Despite the fact that the many risks are well known, some 12.3 percent of expectant mothers continue to smoke, with the majority unable to quit (or prone to relapse within six months).

“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.”

For the study, researchers analyzed data from a large national birth cohort of pregnant women involved in the Finnish Prenatal Study of Schizophrenia. They also checked infant data using the Finnish Maternity Cohort, which had gathered about a million prenatal serum specimens since 1983, and the Finnish Hospital and Outpatient Discharge Registry, which listed all recorded diagnoses for psychiatric issues. The researchers found that 20 percent of schizophrenia cases involved a mother who had a higher level of cotinine (a nicotine marker) in her blood, compared to only 14.7 percent of control cases.

“These findings underscore the value of ongoing public health education on the potentially debilitating, and largely preventable, consequences that smoking may have on children over time,” Brown said. “Future studies on maternal smoking and other environmental, genetic, and epigenetic factors, as well as animal models, should allow identification of the biological mechanisms responsible for these associations. Finally, it is of interest to examine maternal cotinine in relation to bipolar disorder, autism, and other psychiatric disorders.”

Indeed, past research has found links between smoking and mental health disorders, from substance abuse and risky behavior to bipolar disorder. Smoking during pregnancy has also been associated with attention deficit hyperactivity disorder, or ADHD. All of this is likely caused by the fact that smoking — whether in the mother or the individual themself — changes brain development and alters cognitive processes like decision-making.

The researchers hope that their results will assist in boosting awareness about the hazards of pregnant smoking, and also help doctors find new ways to help expectant mothers quit.

Source: Brown A, et al. American Journal of Psychiatry, 2016.