Weed-Smoking Teens 60 Percent Less Likely to Finish High School, Study Says

Literally the largest joint ever
Demonstrators smoke a giant joint of cannabis during a pro-marijuana legalization march in Brasília, Brazil, on May 23, 2014. Ueslei Marcelino/Reuters

According to a new set of studies published in a paper in the British journal The Lancet Psychiatry, teenagers who smoke pot daily are 60 percent less likely than nonusers to finish high school. The studies of adolescent cannabis use also show that daily users under age 17 were 60 percent less likely to finish college than teens who didn't smoke at all, seven times more likely to attempt suicide and eight times more likely to use illegal drugs at some point in their lives.

Investigators recruited 3,725 students in New Zealand and Australia and studied their development from age 13 until age 30 for the three long-term studies that make up the paper. Researchers used the three wide-reaching studies to increase the sample size of participants and convey the statistics more accurately.

The studies took into consideration the sex, age, ethnicity and socioeconomic status of participants, as well as their history of drug use and mental illness. When observing their subjects, the researchers divided them into five levels of cannabis use, ranging from 0 (never using the drug) to 4 (daily use). Then the researchers cross-referenced the subjects' educational habits, noting whether they completed high school and/or college, and also measured symptoms of heavy marijuana use in the past year.

The results, according to the paper, showed "clear and consistent associations between the frequency of adolescent cannabis use and all adverse young adult outcomes." In addition, the research found that the risks associated with smoking marijuana increased significantly depending on levels of use. So those who never used marijuana were most likely to finish high school, and those who used even "low levels" of marijuana once a month were prone to a slew of negative outcomes, including not finishing school and contemplating suicide. Speaking to The Washington Post, Edmund Silins, co-author of the paper, said that "the results suggest that there may not be a threshold where [cannabis] use can be deemed safe" for teenagers.

Which is why the authors argue in the paper that "in the rapidly changing political and legislative landscape, protection of adolescents from the potentially adverse effects of cannabis use is an important facet of cannabis legislative reforms."

Of course, all this is not necessarily news. Robin Murray, a professor at King's College London's Institute of Psychiatry, Psychology and Neuroscience, told Business Insider that "none of the findings will surprise mental health workers, and indeed previous studies have reported similar findings for each of the outcomes separately."

Nevertheless, the long-running study is a significant step forward in better understanding the long-term effects of cannabis use. Thus far, researchers have run into obstacles when trying to study the drug's long-term effects, as it is illegal in most states and they must obtain approval from the Drug Enforcement Agency to study marijuana's medicinal properties and adverse effects alike.