*The following is excerpted from an online article from PsychCentral.
Using marijuana as a teenager may negatively affect educational attainment, new findings suggest. About seven percent of U.S. high school seniors are daily or near-daily cannabis users, and surveys indicate that use is increasing.
Dr. Edmund Silins of the University of New South Wales, Australia, and colleagues explain that, "Persisting questions about the long-term effects of adolescent cannabis use have clouded debate. The existing evidence has limitations, and so the picture of adolescent cannabis use and its putative health consequences is fractured."
In order to address the risk of cannabis on "important domains of well-being during the transition to adulthood," the team recently carried out a study of 3,765 marijuana-using participants from three large, long-term studies based in Australia and New Zealand. Analysis took into account 53 related factors such as age, sex, ethnicity, socioeconomic status, use of other drugs, and mental illness.
This showed "clear and consistent associations" between frequency of marijuana use during adolescence and most of the outcomes investigated: completing high school, obtaining a university degree, cannabis dependence, use of other illicit drugs, suicide attempt, depression, and welfare dependence.
These risks increased with increasing dose, with those who used marijuana daily facing the highest risks.
Those who were daily users of marijuana before the age of 17 were more than 60 percent less likely to finish high school or obtain a degree than those who never used it. Daily marijuana users in adolescence were also seven times more likely to attempt suicide, had 18 times the risk of marijuana dependence, and were eight times as likely to progress to other illicit drugs.
The study findings are published in The Lancet Psychiatry.
Said Silins, “Our results provide strong evidence that the prevention or delay of cannabis use is likely to have broad health and social benefits. Efforts to reform cannabis legislation should be carefully assessed to ensure they reduce adolescent cannabis use and prevent potentially adverse effects on adolescent development.”
The authors believe there are several aspects of the study that support a causal relation: There are strong associations between marijuana use and all young adult outcomes; there is a dose-response association with increasing use; and most associations were not explained by potential “confounding” factors such as mental health problems.
The researchers feel confident that their findings are also relevant to young people in other high-income countries (e.g. the U.S., Canada, and the U.K.) but they make the point that “the social and legislative context of cannabis use varies between regions, and remains an important consideration in the generalization of these findings.”