Scientists Find Biological Link Between Smoking Mothers, Attention Disorders

Need a good reason to quit smoking during pregnancy, aside from the prospect of cancer, lung and heart disease, stillbirth, infertility, and low birth weight?

In what could have far-reaching implications for treatment, scientists at Yale University have found that nicotine exposure during pregnancycan trigger long-term genetic changes in unborn babies.

These newfound genetic changes help explain why maternal smoking has been linked to a host of behavioral issues, such as ADHD.

Nicotine and genetics

Population studies have previously shown that smoking in pregnant women appeared to increase the risk of attention deficit hyperactivity disorder, or ADHD, in children.

This new research is the first time scientists have discovered the biological pathway that causes the increased risk.

The study was done by Yale investigators and is published in Nature Neuroscience.

Marina Picciotto, a professor of psychiatry at Yale University in New Haven, Connecticut, is the paper's senior author. Picciotto says there's a critical point in fetal brain development that appears to be affected by nicotine exposure.

For the study, mice were tested to see if nicotine changes the way fetal brains develop.

"If we expose mice to nicotine during the same window of brain development that is affected in utero in humans," she asked, "can we see changes in the brain? And the answer is yes, we see very long-lasting changes of the nerve cells of the cortex."

In addition, she told VOA, these changes in the neurons were maintained even in adult mice.

Brains and behavior

And how do those changes in the brains of mice affect their behavior? After exposure to nicotine, the mice appear to have ADHD, according to Picciotto.

Normal mice, she says, usually ignore a very mild foot shock. But the nicotine-affected mice, "they just actually pay attention. They are paying attention to a stimulus that is normally screened out."

Investigators also are looking at whether the same genetic pathways are involved in Asperger's syndrome and autism, which can severely impact attention and executive functioning. So far, Picciotto says, there's no evidence of that.

Potential treatment

With the genetic changes pinpointed, the next question is whether the problem can be fixed. Picciotto says that may be possible one day.

"If we are able to block the ability of nicotine to induce these molecules, then can we also block the ability of nicotine to change the structure of these nerve cells and change behavior," she said.

But she also says that, because attention disorders seem to have a genetic component, "there may be abnormalities in this pathway in individuals with attentional dysfunction that is not due to nicotine exposure."

That's the focus of her work going forward. 

"The other thing that I think will hopefully come out of this is whether we can then go and alter ... the function of these pathways," she said. "It would be really very useful to be able to change those molecular pathways ... and see if we can reverse it after the fact."