The health effects of smoking cigarettes have been the subject of scientific study for decades. There’s no doubt the habit impairs the health of the smoker but a growing body of evidence proves smoking harms non-smokers, too. When smokers are pregnant, the children they carry experience the chemicals in the smoke and it affects them accordingly. A new study provides “reliable” evidence that the children of mothers who smoked while pregnant are more likely to exhibit poor impulse control and be thrill-seekers as adults than are the children of non-smokers.

Nathalie Holz, of the Mannheim / Heidelberg University in Germany, led the study of 178 mothers and their child from pregnancy until the child turned 25 years old. All mother-child pairs in the study were residents of Mannheim. Seventy-three of the children were males. Of the mothers:

    •    140 did not smoke cigarettes during pregnancy
    •    38 did smoke during pregnancy

The smoking mothers were divided into two groups:

    •    14 who smoked 1 to 5 cigarettes a day during pregnancy
    •    24 who smoked 5 or more cigarettes a day

Tests for symptoms of attention-deficit/hyperactivity disorder (ADHD) were administered to each child at age 3 months and then again periodically from the time the child was 2 years old until s/he was 15. One significant symptom of ADHD is poor impulse control.

At age 19 years, each child was tested for novelty (thrill) seeking behaviors. Uninhibited thrill-seekers accept more risk when making decisions; the behavior reflects on the person’s ability to control impulses. At age 25, a functional magnetic resonance imaging scan was done to document brain activity.

The brains of the adult children of women who smoked during pregnancy exhibited decreased activity in the areas of the brain that govern impulse control than the adult children of non-smokers; they were more likely to make risky decisions. The children of smokers also exhibited more symptoms of ADHD throughout their childhoods and were more likely to behave on impulse as young adults.

Holz says of her study, “What’s quite surprising is to find such a reliable effect of prenatal smoke exposure that occurred 25 years before.”

Of Holz’s study, Pradeep Bhide says, “This clearly shows that pregnant women smoking is associated not with just ADHD behavior but other impulsivity behavior.” Bhide, a specialist in brain development at the Florida State University College of Medicine in Tallahassee, was not involved with the Holz study but his own studies result in similar findings. His studies have even linked smoking during pregnancy to increased risk of ADHD in the smoker’s grandchildren

Source: Holz, Nathalie E, MA, et al. “Effect of Prenatal Exposure to Tobacco Smoke on Inhibitory Control: Neuroimaging Results From a 25-Year Prospective Study.” JAMA Psychiatry. American Medical Association. May 14, 2014. Web. Jun 8, 2014.