The study published on Tuesday in the journal PLOS Biology showed that a father's exposure to nicotine might cause cognitive deficits in his children and even grandchildren.

The study in mice revealed that the effect was due to epigenetic changes in key genes in father's sperm, or heritable changes that occur without a change in the DNA sequence.

Previous research showed that exposure of mothers to nicotine and other components of cigarette smoke was a significant risk factor for behavioral disorders, including attention deficit hyperactivity disorder, (or ADHD) in multiple generations of descendants.

But the link is less clear for fathers, in part because it has been difficult to separate genetic factors from environmental factors in human studies.

The researchers from Florida State University in Tallahassee exposed male mice to low-dose nicotine in their drinking water during the stage of life in which the mice produce sperm. They then bred these mice with females that had never been exposed to nicotine.

The findings showed that, while the fathers were behaviorally normal, both sexes of offspring displayed hyperactivity, attention deficit, and cognitive inflexibility.

Also, when female (but not male) mice from this generation were bred with nicotine-naive mates, male offspring displayed fewer, but still significant, deficits in cognitive flexibility, according to the study.

Sperm analysis from the original nicotine-exposed males indicated that promoter regions of multiple genes had been epigenetically modified, including the dopamine D2 gene, critical for brain development and learning.

"The fact that men smoke more than women makes the effects in males especially important from a public health perspective. Our findings underscore the need for more research on the effects of smoking by the father, rather than just the mother, on the health of their children," said Pradeep Bhide, co-author of the paper.