Cannabis And Schizophrenia

Obama Admin. Unveils New Policy Easing Medical Marijuana Prosecutions

Those of us who favor legalization should not dismiss some of the risks associated with cannabis use. We devoted a chapter in our collection, “The Cannabis Closet” to those risks and potential harms. And one of them is the relationship between heavy marijuana use among teens and subsequent schizophrenia. The studies are small but definitely add to the case that pot-smoking should be restricted to adult use, especially if there is a family history of mental illness:

A 2007 study in the Lancet, a British medical journal, concludes that using marijuana increases the risk of young people developing a psychotic illness, such as schizophrenia. This risk is greatest—up to a 200% increase—among those who use marijuana heavily and who start using at a younger age.

There are, however, some obvious caveats. First off, do teens with psychological issues self-medicate first with pot? In other words, is the pot-use a sign of early schizophrenia rather than the other way round? Mark Kleiman takes a few steps back:

Those in pre-Boomer and early Boomer birth cohorts in the U.S. – anyone born before about 1952 – had essentially zero experience with cannabis before the age of 18. But that changed rapidly. More than 10% of the high-school seniors of 1979 – roughly speaking, the birth cohort of 1961 – were daily or near-daily pot-smokers. Then the prevalence of heavy adolescent use fell sharply for a little more than a decade, reaching its trough around 1992, and has rebounded since. Yet the rate of schizophrenia diagnosis shows no corresponding cohort-to-cohort swings. (Nor, for that matter, between high- and low-cannabis-prevalence areas within the U.S. or cross-nationally.)

Then there’s the more central question: would legalizing cannabis help or hurt this population? One way I believe that legalization can help avoid this is that under a legal regime, the drug really could be prevented from being so easy to purchase by teens. Right now, it’s easy – and there’s no way to know exactly what you’re getting. High CBD strains might be an option to minimize harm – but keeping pot away from teens may well be better achieved by legalization rather than continuing Prohibition.

But let’s say the risk increases for those kids.

It seems absurd to say that wider cannabis consumption wouldn’t have some costs. The real question is: compared with what? Kleiman again:

Note, for example, that people put in jail or prison are at risk of severe damage, especially if while inside they become victims of physical or sexual assault. Some commit suicide. So the mental-health costs of arresting 650,000 people a year, and holding 30,000 or more prisoners at any one time, for cannabis offenses – costs that would be largely, though not entirely, abolished by legalization – might easily match or exceed the mental-health costs of increased exposure to cannabis.

All substances – alcohol and cigarettes come to mind immediately – can cause harm as well as good. My own view is that more cannabis use would improve our society in many ways. But I cannot know that for sure. What we need is a sober weighing of pros and cons, rather than context-free scare stories. But fear is what sustains Prohibition, so it is unsurprising that it is a tool deployed by the once libertarian WSJ Op-Ed page.

(Photo: David McNew/Getty)