If your mother smoked, you're more likely to be an aggressive kid, according to a new Canada-Netherlands study published in the journal Development and Psychopathology.

And mothers who smoke, give birth under 21 and are poor should have caused North American to be overrun by the societal equivalent of Middle East dictators by now -  so take what you want from that.  While previous studies have shown that smoking during gestation causes low birth weight, this research claims mothers who light up during pregnancy predispose their offspring to an additional risk: violent behavior. 

As mentioned above, the research team also says the risk of giving birth to aggressive children increases among smoking mothers whose familial income is lower than $40,000 per year.

Farther in, they finally mention the risk factor for aggressive behavior in offspring most likely to be the case;  mothers with a history of antisocial behaviour: run-ins with the law, high school drop-outs and illegal drug use.   Smoking is often common in that group too.

Psychiatry professor and researcher Jean Séguin, of the Université de Montréal and Sainte-Justine Hospital Research Center, co-authored the study with postdoctoral fellow Stephan C. J. Huijbregts, now a researcher at Leiden University in the Netherlands, as well as colleagues from Université Laval and McGill University in Canada.

"Mothers-to-be whose lives have been marked by anti-social behaviour have a 67 percent chance to have a physically aggressive child if they smoke 10 cigarettes a day while pregnant, compared with 16 percent for those who are non-smokers or who smoke fewer than 10 cigarettes a day," says Dr. Séguin. "Smoking also seems to be an aggravating factor, although less pronounced, in mothers whose anti-social behaviour is negligible or zero."

The research was carried out as part of a wider investigation of children, the Quebec Longitudinal Study, which examined behaviors of 1,745 children between the age of 18 months to three and a half years. Aggressive offspring were characterized by their mothers as quick to hit, bite, kick, fight and bully others. 

Other risks for aggressive behavior

Although physical aggression is most common in preschool children, the researchers identified other prenatal factors associated with aggressive behavior in children: mothers who are younger than 21, who smoke and who coerce their children to behave. The researchers also found that children from families who earned less than $40,000 per year were at an increased risk for aggressive behavior. 

In this category, heavy smokers had a 40 percent chance of having highly aggressive children, compared with 25 percent for other mothers who were moderate or non-smokers. When income was greater than $40,000 annually, the gap between heavy smokers and others fell to 8 percent. 

The effect of smoking on aggression in offspring remained significant – even when other factors were removed such as divorce, depression, maternal education and the mother's age during pregnancy. Smoking during pregnancy is one factor that could be curbed to decrease risks of aggression and violent behavior.

The research team recommends that low-income women, who are heavy smokers and who have a history of anti-social behavior become a screening criterion for prenatal testing to determine what families need extra support to prevent development of aggressive behavior.