If you need another reason not to light up while pregnant, here it is: A new study finds that children born to mothers who smoked while pregnant were more likely to end up on psychiatric medications such as antidepressants and stimulants by age 20, Reuters reports.

Published in the American Journal of Epidemiology, the study looked at data on 175,000 children born in Finland, including whether their moms smoked while pregnant.

The researchers also used a national insurance database of prescription drugs for the period when the children were 5 to 20 years old.

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.

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