Adolescents and young adults who use electronic cigarettes are far more likely to also use marijuana, according to research released this week. The study, published online this week in JAMA Paediatrics, said the odds of marijuana use among young people who used e-cigarettes was 3.5 times greater than among those who said they had not used e-cigarettes. The research examined marijuana use among 10- to 24-year-olds through a compilation of 21 studies from the United States, Canada, Europe, Australia, and New Zealand.