Teenagers who begin smoking at an early age are much more likely to start using marijuana by the time they're 17, researchers report.
The researchers also found that starting smoking at an early age was an especially strong predictor of drug use. Participants who started smoking by age 12 or earlier were 26 times more likely to start using drugs by age 17 than those who never smoked.
Cigarettes lead to drug use
"The findings support the gateway hypothesis, which asserts that illicit substances such as tobacco and alcohol are a stepping stone to harder, illicit drugs," project team member Tellervo Korhonen, of the University of Helsinki, said in an Academy of Finland news release. The academy funded the project.