Researchers analyzed data of over 2,000 children from the time they were born to when they were 10 years old. The data collected by Quebec health authorities and also included details from parents regarding their exposure to second hand smoke while the teachers were asked about the children's behavior in class.
The researchers found that children who were exposed to second hand smoke displayed aggressive behavior by the time they were in fourth grade.
"Secondhand smoke is in fact more dangerous than inhaled smoke, and 40 percent of children worldwide are exposed to it. Moreover, exposure to this smoke at early childhood is particularly dangerous, as the child's brain is still developing", lead researcher Dr Linda Pagani said.