Despite the fact that 33 states have legalized marijuana in some form, data from at least one source shows that the rate of teenage use has not increased. Since 2005, the amount of 12th graders who have tried cannabis at least once hasn’t changed, at least in Monitoring the Future’s dataset. Instead, the number has pretty much remained below 45 percent.
That’s a good thing, particularly in light of a new study that found that teens who use cannabis have a higher risk of developing depression as young adults. Published in the journal JAMA Psychiatry, the study found that teens who used marijuana at least once a week before the age of 18 were associated with a 37 percent increased risk of depression as adults. Scientists found this was true even when taking into account someone’s previous mental health history.
Researchers from Oxford and McGill Universities came to these conclusions by analyzing 11 studies that included just under 24,000 teenagers. From that analysis, they estimated that teen cannabis use could be associated with nearly 400,000 cases of depression.
As always, it’s important to note that the results show associations and not causal links, and are still based on only 11 studies. The researchers screened over 4,000 papers before finding the few that specifically tracked marijuana use and mental health starting in adolescence. Additionally, the studies didn’t provide information on how much cannabis the teens smoked, or the potency. Considering that the subjects were teens decades ago, when marijuana was much less potent, that is one big omission.
“The results have to be interpreted with caution because it’s based on a very small number of published studies, but the signal is quite strong,” Guohua Li, an epidemiologist at Columbia University’s Mailman School of Public Health not involved with the study, told The Verge. “The implications of the study for public policy and mental health are profound,” he adds, as Monitoring The Furniture’s dataset also shows that about 20 percent of high school seniors use cannabis monthly.
Studies like this are important when considering cannabis legalization efforts. Why? Two reasons. First, establishing proper legal age limits for cannabis use and second, showcasing why legalization is necessary to allow more research like this. Only by properly studying the plant will we learn how also to properly use it.