Prenatal Smoking Linked To ADHD In Offspring

Prenatal Smoking Linked To ADHD In Offspring

Prenatal exposure to tobacco smoke appears to lead to alterations in the brain similar to those seen with attention-deficit/hyperactivity disorder (ADHD), a new study shows. adhd-prenatel-smoking-link

Using functional magnetic resonance imaging (fMRI), researchers from the Central Institute of Mental Health, Mannheim/Heidelberg University, Germany, showed that young adults exposed to tobacco smoke in utero had less activity in brain regions known to be involved in inhibitory control relative to their peers without this exposure.

“These findings point to a functional involvement of prenatal exposure to tobacco smoke in neural alterations similar to ADHD, which underlines the importance of smoking prevention treatments,” the authors, led by Nathalie E. Holz, write.

The study was published in the July issue of JAMA Psychiatry.

The Smoking – ADHD Link

There is a well-documented link between smoking during pregnancy and externalizing disorders such as ADHD, although the neurobiological underpinnings of why are unclear.

Only a small number of studies have assessed the long-term neural consequences of smoking during pregnancy for the offspring; most of these studies concentrated on structural changes, with mixed results. Research such as this study on the effect of maternal smoking on a functional level is rare.

The investigators designed the study to clarify the effect of prenatal tobacco exposure on the neural activity in the inferior frontal gyrus (IFG) and the anterior cingulate cortex (ACC), areas important to inhibition control.

Data for the study came from a community sample of 178 mothers and their healthy adult offspring (73 males) who were followed since birth. Fourteen mothers (7.9%) reported smoking 1 to 5 cigarettes per day during pregnancy, 24 (13.5%) smoked more than that amount, and the rest were nonsmokers (78.7%).

The offspring underwent fMRI at age 25 years during a modified Eriksen flanker/NoGo task, which measures inhibitory control. ADHD symptoms were assessed during a period of 13 years (from age 2 to 15 years).

Mothers Smoking While Pregnant Causes Long-term Harm In The Child

Compared with adults with no prenatal tobacco exposure, those who had mothers that smoked exhibited significant decreased activity in the above noted brain areas during testing (ACC, IFG and supramarginal gyrus. They also had decreased volume in the right IFG.

The study team also found an inverse relationship between IFG activity and ADHD symptoms; adults with prenatal tobacco exposure showed more ADHD symptoms between ages 2 and 15 years relative to their peers without prenatal tobacco exposure. There was also an inverse link between ACC activity and novelty seeking.

These findings “suggest that smoking during pregnancy may have widespread long-term effects on neural activity and development independent of prenatal and postnatal adversity, as well as substance abuse, among the offspring,” the investigators conclude.

“Therefore, our findings strengthen the importance of smoking cessation programs for pregnant women and women planning to become pregnant, to minimize prenatal exposure to tobacco smoke by the offspring,” they add.

JAMA Psychiatry. 2014;71:786-796. Abstract

Take away from this study is that repeated episodes of hypoxia (low/inadequate oxygen) for the growing unborn baby can and does cause brain damage.