Smoking Throughout Pregnancy May Have Long-Term Effects on Offspring’s Brain Development

Smoking throughout pregnancy appears to have lasting effects on the brain development of the offspring, suggests a study of children aged 9 to 11 years published today in JAMA Network Open. Specifically, the study found that continued exposure to maternal tobacco use in utero was associated with lower brain volume.

“[I]nterventions targeting maternal smoking cessation before pregnancy or in early pregnancy may favor normal brain development among children in the long term,” wrote Runyu Zou, Ph.D., of Erasmus University Medical Center Rotterdam and colleagues.

The researchers analyzed data collected as part of the Generation R Study—a prospective population-based study in Rotterdam, the Netherlands, of 9,778 women who gave birth between April 2002 and the end of January 2006. They focused on the MRI data from 2,704 children (average age, 10 years) and the information on tobacco use during pregnancy provided by children’s parents. Mothers were asked about their tobacco use at the time of study enrollment as well as in each trimester; fathers were asked about their tobacco use at the time of study enrollment only. The researchers categorized maternal tobacco use during pregnancy into one of three categories: never during pregnancy, until the pregnancy was known, and continued during pregnancy.

Of the 2,704 mothers in the study, 77.7% never smoked during pregnancy, 13.5% continued smoking throughout pregnancy, and 8.8% stopped smoking after becoming aware they were pregnant (mostly in the first trimester). Children born to mothers who continued smoking during pregnancy showed lower total brain volume as well as lower cerebral gray matter and white matter volume compared with children born to mothers who never smoked during pregnancy, Zou and colleagues wrote. The children exposed to maternal smoking throughout pregnancy also had smaller surface area and less gyrification (the folding of the cortex) compared with the unexposed children. The brain differences seen in children exposed to maternal smoking throughout the pregnancy were not seen in the children born to mothers who stopped smoking early in pregnancy.

“These associations were not explained by paternal smoking nor mediated by smoking-associated DNA methylation patterns at birth,” the authors reported.

“All efforts should be made to help pregnant women quit smoking as well as to stop the use of all other nicotine-containing products before pregnancy or as early as possible during pregnancy,” Mikael O. Ekblad, M.D., Ph.D., of the University of Turku in Finland wrote in an accompanying editorial. “The goal should not only be smoke-free but also nicotine-free pregnancy … .”

For related information, see the American Journal of Psychiatry article “Nicotine Use and DSM-IV Nicotine Dependence in the United States, 2001–2002 and 2012–2013.”

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Heavy Drinking in Adolescence Appears to Change Developing Brain

Initiating heavy drinking of alcohol during adolescence appears to alter normal brain development, suggests a study in the April issue of the American Journal of Psychiatry.

It is well known that during adolescence the brain undergoes significant changes—marked by decreases in gray matter (neuronal cell bodies, dendrites, unmyelinated axons, and synapses) and increases in white matter (myelinated axons that coordinate signals between neurons). To examine the effects of alcohol consumption on neurodevelopment, Adolf Pfefferbaum, M.D., of SRI International and colleagues compared structural MRI data from 483 youth aged 12 to 21 before the initiation of drinking and at follow-up one and two years later. Youth were also asked about their alcohol and marijuana use at each follow-up.

“At baseline, all participants met the study-entry criteria for no or low drinking and drug use,” Pfefferbaum and colleagues wrote. (No/low drinkers reported drinking less than one time per month, less than two drinks on average, and less than four drinks maximum). “As anticipated, however, a proportion of these youths (n=127) initiated drinking to levels that exceeded, to varying degrees, the study entry criteria, thereby enabling pursuit of a naturalistic study on the effects of drinking on the adolescent brain.”

At the two-year follow-up, 356 youth continued to meet the study’s no/low drinking criteria and 127 youth transitioned from the no/low drinking group to one of two drinking groups: 65 moderate drinkers and 62 heavy drinkers (see online data supplement for descriptions of alcohol consumption in heavy and moderate drinkers).

The authors found that while no/low drinkers experienced reductions in gray matter and increases in white matter over time, “[v]olumes of frontal, cingulate, and total gray matter declined more rapidly and central white matter expanded more slowly in the heavy drinkers than in the no/low drinking group.”

In an accompanying editorial, Jennifer L. Stewart, Ph.D., of Queens College, City University of New York, pointed out: “It is important to note that baseline gray and white matter volume alone did not differentiate the alcohol use groups, which suggests that the differences in brain structure were not present before onset of heavy alcohol use. On the contrary, increases in alcohol consumption paralleled aberrant structural brain changes over the two-year period, providing evidence supporting the idea that gray and white matter derailment is indeed present at early stages of problem alcohol use.”

“What we’re seeing here is an alteration in normal development,” Pfefferbaum said in the April AJP audio podcast. “When we did this study, we saw that children as young as 12 sometimes start drinking.” Clinicians should be sure to ask youth about alcohol and other drug use, just as they do adults, he said.

(Image: Triff/Shutterstock)

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