Kids who smoke more likely to toke, marijuana study says

(CBS) Does smoking tobacco fuel the "need for weed?"

Maybe so. Finnish researchers have just completed a study that identifies early tobacco use as a major risk factor for using marijuana.

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By their seventeenth birthdays, about 15 percent of girls and 12 percent of boys who participated in the study had smoked pot or used another illicit substance at least once, the study showed. Pot smoking was more common in girls and in boys who exhibited aggressive behavior, as well as in kids who binged on alcohol or had fathers who did and those whose peers smoked or used drugs.

But kids who smoked tobacco at an early age were especially likely to be using pot by age 17.

Just how strongly does early tobacco smoking predict pot smoking? Compared to children who never smoked, kids who had started smoking by age 12 were 26 times more likely to start using drugs by age 17.

"The findings support the gateway hypothesis, which asserts that licit substances such as tobacco and alcohol are a stepping stone to harder, illicit drugs," Tellervo Korhonen, one of the researchers who conducted the study, said in a written statement released by the the Academy of Finland, which supported the research.

The study was published in the Journal of Child and Adolescent Psychiatry.