Need another reason not to smoke? Your grandchildren

“Where there’s smoke, there’s fire” is a phrase that’s been around for a long time; it means that if it looks like there’s something wrong, then there probably is. So picture a pregnant woman smoking. What’s wrong with this picture? Maybe more than you think: She’s putting her daughter’s daughter at risk for autism spectrum disorder!

A recent study from the University of Bristol has shown some pretty conclusive epidemiological evidence that grandmothers who smoked while they were pregnant saw greatly increased rates of ASD in their granddaughters.

As strange as that sounds, listen to this:

The university researchers looked at 14,500 participants of the Children of the 90s Study and found that if a girl’s maternal grandmother smoked during pregnancy, she was 67 percent more likely to display behaviors linked to autism, such as poor communication skills and repetitive behaviors, and she had a 53 percent increased risk of landing squarely on the spectrum.

Paternal grandmothers smoking during pregnancy showed no associations.

How could this happen? The researchers offered two possible explanations. DNA damage caused by smoking is transmitted to the grandchildren, or it alters the grandchildren’s gene-moderated response to an environmental pollutant that they happen to encounter. Something like a hormone disruptor in plastics (BPA), a pesticide (glyphosate used on GMO crops) or a combination of environmental pollutants. And that cascade leads to ASD problems.

Bottom line: Male, female, young, old, don’t smoke—anything.

Once researchers go back another generation, they might find that the original problem was great-grandpa smoking.