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A reader writes:

Frum's suggestion that pot is the true culprit in the Tucson massacre is ridiculous on its face. My daughter has been hospitalized three times due to psychotic breaks, so I know that many things can trigger such an episode. Copious amounts of marijuana, sure. Alcohol even more so, and with much more moderate usage. Any mind-altering substance used recreationally is dangerous for the mentally ill, but fasting or having one's sleep disrupted can also trigger psychotic breaks. Frum's post is a truly laughable red herring.

Another dissents:

This weekend you dedicated post after post to the idea that the right wing, and Sarah Palin in particular, share a small portion of the blame for the Tucson attack because they have fostered a political climate of hate through their charged and occasionally violent rhetoric. Yet when David Frum suggests that marijuana may have had a role to play in the attack, you sarcastically dismiss it. You scoff, "Frum goes there...", as if it is a ludicrous suggestion.

I share your worldview in a lot of ways, but I think you've got this one completely upside down.

The alleged killer seems to be a mentally disturbed individual, possibly schizophrenic, who has no discernible political ideology and no connection I know about to Palin or the right wing. I think the answer to the question of whether Palin bears any responsibility at all for this attack is - based on what we know at present - "no, not at all".

On the other hand, I think it's undeniable that this individual's disturbed mental state played a serious role in the attack. Witnesses suggest he smoked a lot of marijuana, and there is strong scientific evidence that shows a correlation, at least, between marijuana and mental problems like schizophrenia. In that context, why is it ridiculous to suggest his weed-smoking could be responsible? If he was an alcoholic, and Frum had suggested his alcoholism could have played a role, I doubt you'd be scoffing. I think it's certainly just as likely that marijuana is to blame here as Palin - probably a lot more likely.

I agree that the right wing has been dangerous with their rhetoric over the last few years. But you need to stop looking at the world through your own limited prisms every single time - "it's Palin's fault", etc.  Sometimes you react with gut instinct instead of reason.

Another writes:

Frum isn't totally off-base here. There is evidence that THC can, in rare cases, induce psychosis in certain people who are susceptible.

But the full story goes deeper than that. While THC itself can act as a psychotic, another chemical in cannabis called cannabidiol or CBD acts as an anti-psychotic, and shows promise in treating schizophrenia symptoms. The result is that the two chemicals seem to balance each other out. What's more, there's only so much of both chemicals that a cannabis plant can produce. So as cannabis plants are bred to produce more and more THC, they also produce less and less CBD, disrupting the balance.

If you were to ask me, the solution isn't to ratchet up the war in soft drugs; the answer is to regulate them. If the state mandates and monitors the acceptable levels of THC and CBD in cannabis, it can ensure that the two forces stay in balance. Yet another reason to legalize.

Another emails the above screenshot:

I was both tickled and horrified by this banner ad on Frum's cannabis post.

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