Many people, including the president of the United States, smoked pot in high school but nevertheless managed to graduate, earn college degrees, and lead reasonably happy and successful lives. If you are one of those people, or if you know some of them, you may be skeptical of a new study linking even occasional adolescent marijuana consumption to academic failure, addiction, and attempted suicide. Maybe you and your friends were just lucky, or maybe these results are misleading. More the latter, it turns out.
The study, reported last week in The Lancet Psychiatry, found that people who smoke pot as teenagers are more likely than people who don't to drop out of high school, become dependent on cannabis, use other illegal drugs, and attempt suicide. The associations were strongest for those who smoked pot the most.
The researchers, led by Edmund Silins of the National Drug and Alcohol Research Centre in Sydney, Australia, found that subjects who smoked pot daily before age 17 (a pattern of use that is far from common) were 63 percent less likely to finish high school than subjects who abstained, 62 percent less likely to earn a college degree, 18 times as likely to be dependent on cannabis as adults, eight times as likely to use other drugs, and seven times as likely to attempt suicide. By comparison, subjects who smoked pot less often than monthly before 17 were 22 percent less likely than nontokers to finish high school, 22 percent less likely to earn a college degree, twice as likely to be dependent on cannabis as adults, 67 percent more likely to use other drugs, and 62 percent more likely to attempt suicide.
Silins et al. call these outcomes "psychosocial sequelae of adolescent cannabis use," and some press coverage of the study likewise has portrayed them as consequences of marijuana consumption. But the causal role of cannabis is not nearly as clear as these accounts imply.
It surely is plausible that teenagers who get stoned every day, like teenagers who get drunk every day, would have trouble doing well in school because they are intoxicated when they are supposed to be learning. But that observation leaves unanswered the question of why some teenagers, but not others, choose to get stoned every day. The propensity to engage in that sort of behavior may be a marker for characteristics that independently undermine academic performance.
The researchers tried to account for that possibility by adjusting their results for various confounding variables—factors other than marijuana use that may contribute to the observed associations. They say they adjusted for 53 confounding variables, which sounds impressively thorough. But their data—based on samples ranging from 2,537 to 3,765 subjects, depending on the outcome reported—are drawn from three different studies in Australia and New Zealand, each of which measured a subset of those 53 variables. The number of variables reported in those studies actually ranged from 14 to 21.
More important, it is unlikely that these measures, which include childhood behavior problems, grades in elementary school, attention difficulties noted by parents, and self-reports of depression and anti-social behavior, adequately account for the combination of apathy, alienation, boredom, frustration, and rebelliousness that might lead a teenager to get high instead of paying attention in school and doing his homework. While intoxication itself may be a barrier to learning, the psychological factors that encourage intoxication probably play a role as well. Likewise, the emotional issues that motivate frequent intoxication, issues that may have gone undetected by the measures used in this study, could make people more prone to suicide.
Such hard-to-measure variables may be especially important in understanding the associations between relatively light cannabis consumption and bad outcomes. While it's quite plausible that a kid who routinely comes to school stoned would have trouble learning the skills and absorbing the information he needs to graduate, it is hard to believe that smoking pot a few times a year would in itself reduce a teenager's odds of graduating by 22 percent, let alone that it would make him 62 percent more likely to attempt suicide as an adult.
Washington Post blogger Christopher Ingraham notes some other complications related to marijuana's legal status and the way pot smokers are treated:
If a teacher knows or even suspects that a certain kid is using drugs, that may predispose the teacher against that student. "Teachers are very likely to stigmatize drug users," says Joseph Palamar, co-author of another recent study comparing teen marijuana and alcohol use. "That stereotype gives kids problems, and that kid's not gonna want to go to class."
Palamar also says that because marijuana "is an illegal drug, you have to buy it in an illegal manner, and then you're exposed to the black market. Marijuana use is affiliating you with other kids, some of whom might be problematic—people more likely to question authority. You become affiliated with things that might have a negative impact on your education."
Moreover, Palamar's research shows that because of marijuana's legal status, teen cannabis users are much more likely to get into trouble with the police than teen alcohol users. And in many cases, if you have a drug conviction on your record, you become ineligible for college aid. "If you get caught with drugs, you're not able to go to college," he told me.
In short, while it is hard to dispute that early and frequent marijuana use can cause problems, such behavior is part of a complicated psychosocial web that is difficult to untangle with the methods used in this study. And while prohibitionists are bound to cite this study as an argument against legalization, the question of whether teenagers should smoke pot is clearly distinct from the question of whether adults who do so (or the people who help them) should be arrested and punished.
As NORML Deputy Director Paul Armentano told HealthDay, "There is little debate among experts that the use of cannabis by young people, in particular daily use of cannabis, ought to be discouraged, just as young people's use of other potentially problematic intoxicants, such as alcohol and tobacco, ought to similarly be discouraged." But that does not mean prohibition is a good way to accomplish that goal. "The presumption that criminalizing cannabis adequately prevents or limits young people from gaining access to cannabis is demonstrably false," Armentano said. "Criminalizing cannabis for adults has little if any impact on reducing teens' access [to] or consumption of the plant."
I am not completely convinced of that last point. Some consequences of legalization—retailers who card, for instance—work against underage consumption. But others, such as lower prices and readier availability for adults who may be willing to share their purchases with minors, could increase underage access. Whatever the net effect, the special vulnerabilities of adolescents do not justify treating adults like children.
[This post originally appeared at Forbes.com.]