Kids and adolescents who use marijuana every day before they reach age 17 are more than 60 percent less likely to finish high school or get an equivalent degree than young people who have never used the drug, according to a new study.

The researchers, from universities in Australia and New Zealand, reviewed three long term studies on youth and teen drug use in those two countries and say the findings are applicable to drug use and outcomes in other countries, including the U.S.

Their review of the data found that young adults who use marijuana every day are also seven times more likely to attempt suicide, are 18 times more likely to be dependent on the drug and are eight times as likely to use other potentially addictive drugs later in their lives as youth who never used marijuana.

“Our findings are particularly timely given that several U.S. states and countries in Latin America have made moves to decriminalize or legalize cannabis [marijuana], raising the possibility that the drug might become more accessible to young people,” says Richard Mattick, Ph.D., senior author of the study and a professor of Drug and Alcohol Studies at the University of New South Wales.

The associations between marijuana use and serious outcomes, such as suicide attempts and failing to finish high school, remained constant even after including more than fifty other risk factors for those outcomes such as sex, ethnicity, socioeconomic status, use of other drugs, and mental illness. The risk of serious consequences of marijuana use increased with higher doses of the drug and for those who used marijuana every day.

“Efforts to reform cannabis legislation should be carefully assessed to ensure they reduce adolescent cannabis use and prevent potentially adverse effects on adolescent development,” says Edward Silins, Ph.D., a research fellow and lead author of the study.

The study was funded by the Australian Government National Health and Medical Research Council and published in the journal Lancet Psychiatry.