Does Weed Cause Schizophrenia?

Over the weekend you might have noticed a MoJo piece about a new book by Alex Berenson called Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence. Stephanie Mencimer says the book “takes a sledgehammer to the promised benefits of marijuana legalization, and cannabis enthusiasts are not going to like it one bit.”

Probably not. But it’s worth noting that although I didn’t notice anything flatly incorrect in Berenson’s claims, there’s nothing all that new about them. And he does overstate the risks, I think. Here’s a very quick roundup of what we know:

  • About 10-15 percent of teens who try marijuana become dependent. This is roughly similar to the rate for alcohol dependency.
  • If you have schizophrenia, marijuana use will make it worse. Anyone with persistent psychotic symptoms should be kept far away from cannabis of any kind.

However:

  • It is far less clear whether regular marijuana use causes schizophrenia. Drug researchers have been studying this for decades, and have concluded that there’s some evidence of a causal effect—but not a strong one. That’s the consensus so far, anyway.
  • For example, marijuana use has increased considerably over the past 20 years, and so has the potency of marijuana. And yet, on a nationwide basis, there’s been no increase in diagnoses of schizophrenia. It affects less than 1 percent of the population, and that’s stayed steady for a long time.

  • Even if marijuana affects the onset of schizophrenia, the real-world effect is probably small. If the risk increases by as much as 40 percent, for example, that’s an increase from perhaps 0.5 percent to 0.7 percent.

Nothing is perfect, and there’s no question that marijuana isn’t harmless. Among other things, no one with schizophrenia should get near the stuff, and if you have a family history of severe mental illness you might want to think twice about using it. That said, the notion that smoking marijuana significantly increases the risk of schizophrenia in the future is not really supported by the literature. There’s probably some risk, but it’s fairly small and the evidence for it is fairly weak.

As with so many other things, though, daily use by teens is generally not a good idea—especially given the extremely high potency of modern pot. Anything that affects brain development even modestly should be used sparingly by teens whose brains are still in the process of maturing. There’s no need to panic, but it’s unquestionable that allowing your teen to become a serious stoner is a bad idea on a whole bunch of levels.

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THE FACTS SPEAK FOR THEMSELVES.

At least we hope they will, because that’s our approach to raising the $350,000 in online donations we need right now—during our high-stakes December fundraising push.

It’s the most important month of the year for our fundraising, with upward of 15 percent of our annual online total coming in during the final week—and there’s a lot to say about why Mother Jones’ journalism, and thus hitting that big number, matters tremendously right now.

But you told us fundraising is annoying—with the gimmicks, overwrought tone, manipulative language, and sheer volume of urgent URGENT URGENT!!! content we’re all bombarded with. It sure can be.

So we’re going to try making this as un-annoying as possible. In “Let the Facts Speak for Themselves” we give it our best shot, answering three questions that most any fundraising should try to speak to: Why us, why now, why does it matter?

The upshot? Mother Jones does journalism you don’t find elsewhere: in-depth, time-intensive, ahead-of-the-curve reporting on underreported beats. We operate on razor-thin margins in an unfathomably hard news business, and can’t afford to come up short on these online goals. And given everything, reporting like ours is vital right now.

If you can afford to part with a few bucks, please support the reporting you get from Mother Jones with a much-needed year-end donation. And please do it now, while you’re thinking about it—with fewer people paying attention to the news like you are, we need everyone with us to get there.

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