The researchers also used a national insurance database of prescription drugs for the period when the children were 5 to 20 years old.
One in 11 kids was prescribed a psychiatric medication at some point during that period, including anti-anxiety drugs, antipsychotics, antidepressants, stimulants and drugs for addiction.
Of kids and teens whose moms didn't smoke during pregnancy, 8 percent were on at least one of those drugs during the study period.
That compared to 11 percent of those whose moms smoked less than 10 cigarettes a day, and close to 14 percent whose moms had lit up more than 10 times per day.
The link remained when researchers left out babies who were born early or very small -- other factors that could affect future mental health.
The study doesn't prove that smoking while pregnant alters the baby's brain. And it's not clear if the problems come from smoke exposure before or after the baby is born. But the researchers suspect smoke affects development.
"At the very least, parents need to be educated that they might be doing brain damage to their children" if they smoke during key times in development, Weitzman said.
He added that doctors should keep this in mind and look out for mental health problems in their young patients.
(image via: http://en.wikipedia.org)