It's been well established that tobacco smoke is bad for kids' lungs but a new study suggests it may also have an affect on their behaviour.
Researchers at the University of Montreal found kids exposed to household tobacco smoke had a higher risk of aggression, behaviour problems at school and anti social behaviour.
The researchers looked at a group of kids born in 1997 and 1998 and whether anyone smoked in the home from when they were 1.5 to 7.5 years old.
Professor Linda Pagani says they tried to control for other factors that could cause the issues including the parents' mental health, income and education.
"It's pretty compelling," Pagani told Moore in the Morning on NEWSTALK 1010. "It's as close as we could get to causality in an associational study."
Pagani says her past studies have shown the neurotoxicity of household smoke.