Photo: telegraph.co.uk

It’s been well established that smoking substantially affects health for more than a century (a bit less than that in official gov records), yet its long term effects on future generations may be more dangerous than anyone might have guessed. The perils of second hand smoke have been proven for a while, but scientists will have a real tough time confirming a most recent hypothesis that links the ever rising cases of ADHD with nicotine intake. To be more precise, the idea involves epigenetics and data so far suggests that it may be possible that some children today grow to develop ADHD because their grandmother had smoked  in pregnancy, even though the actual mother never smoked.

It’s really fascinating, and if some may find the idea of smoking inflicting genetic changes for generations to come , read on and you might find it plausible as well. Attention deficit hyperactivity disorder (ADHD) is a common condition that affects children and adolescents and can continue into adulthood for some.The National Institute of Mental Health (NIMH) estimates that 3% to 5% of children have ADHD. Some experts, though, say ADHD may occurs in 8% to 10% of school-aged children. Children with ADHD generally have problems paying attention or concentrating. They can’t seem to follow directions and are easily bored or frustrated with tasks. They also tend to move constantly and are impulsive, not stopping to think before they act.

From grandmother to grandchild

Pradeep G. Bhide and Jinmin Zhu, both researchers at Florida State University, believe they have evidence that ADHD induced by nicotine can be passed across generations. Doctors know for some time that drinking and smoking during pregnancy can cause ADHD, but the present research discusses the possibility of ADHD as  an environmentally induced health condition. Previously, it was shown that nicotine can leave permanent marks on the genome which make future offspring more susceptible to respiratory conditions.

“What our research and other people’s research is showing is that some of the changes in your genome – whether induced by drugs or by experience – may be permanent and you will transmit that to your offspring,” said Bhide.

Building on this sort of research, like studies that showed stress and fear can be genetically passed on to future generations, the Florida State scientists  found a link between prenatal nicotine exposure and hyperactivity in mice. Their data, however, suggest that there is a transgenerational transmission via the maternal, but not the paternal, line of descent.

“What’s important about our study is that we are seeing that changes occurring in my grandparents’ genome because of smoking during pregnancy are being passed to my child,” says Bhide. “So if my child had ADHD it might not matter that I did not have a disposition or that I never smoked.”

The exact causes of ADHD are widely debatable, but what scientists do know for sure is that it’s somehow genetic, seeing how ADHD parents are more likely to foster ADHD children. The past few decades has seen an alarmingly high increase in ADHD cases, and various explanations have been sought. The researchers speculate on their findings and claim  one possible contributing factor in the current spike in ADHD cases  is the rising number of women who picked up smoking following the second world war or today grandmothers.

“Genes are constantly changing. Some are silenced and others are expressed, and that happens not only by hereditary mechanisms, but because of something in the environment or because of what we eat or what we see or what we hear,” Bhide said. “So the genetic information that is transmitted to your offspring is qualitatively different than the information you got from your parents. The next question is how does transmission to future generations happen? What is the mechanism? And the second question is, if the individual is treated successfully would that stop the transmission to future generations?”

Findings appeared in  The Journal of Neuroscience.