Although the number of women who smoke during pregnancy in Los Angeles and throughout the U.S. has dropped in recent years, a significant number of women smoke during pregnancy. According to an August 2010 Finnish study, the risk for psychiatric illness is significantly higher in young adults who were exposed to cigarette smoke in the uterus when compared to those who were not. Study author Mikael Ekblad, of University of Turku, Finland, stated, “This association seemed to be robust because it could be found in a large group of diagnoses and the dose relationship was also strong.” He added that prenatal smoking exposure impairs fetal growth and modulates brain development, which may alter mental development of the offspring.
The researchers reviewed data from 175,869 Finns born from January 1, 1987 through December 31, 1989. They underwent 18 to 20 years of follow-up to evaluate the effects of prenatal smoking exposure on psychiatric illness. The researchers had self-reported information on the mothers’ smoking habits during pregnancy and other relevant background factors, including the psychiatric history of the mothers and their children.
A total of 26,075 mothers (15.3%) smoked during pregnancy. Of these, 8,866 (34.0%) smoked more than 10 cigarettes a day. In 5,487 cases (3.2%), maternal smoking history was unknown.
The prevalence of any psychiatric diagnosis was 15.0% after excluding the children with unknown maternal smoking history. The prevalence was 13.7% in unexposed children (the control group), 21.0% in those exposed to fewer than 10 cigarettes a day, and 24.7% in those exposed to more than 10 cigarettes a day.
With the exceptions of schizophrenia and anorexia nervosa, prenatal smoke exposure significantly increased the risk for most psychiatric illnesses. The strongest effects were seen for psychiatric disorders due to psychoactive substance use and behavioral and emotional disorders. The authors noted that the lack of a statistically significant finding for schizophrenia may be due to a fairly low number of cases in the study. A total of 870 deaths occurred in the study population (5.7 per 1000), of which 64 (7.4%) were suicides. Young adults exposed to more than 10 cigarettes a day during gestation had a significantly increased risk for early death compared with unexposed young adults. The mortality rate per 1,000 children was 4.7 for unexposed children; it was 6.3 for those exposed to less than 10 cigarettes a day and 9.1 for exposure to more than10 cigarettes per day.
