A new study identifying minor differences in the brain imaging of habitual marijuana consumers compared to non-users may be ideal for stimulating sensational headlines (e.g., “Regular pot smokers have shrunken brains, study says,” Los Angeles Times, November 10), but tells us little in regard to whether pot poses actual health risks.

Specifically, an MRI scan revealed less gray matter in the orbital frontal cortex of pot-smoking subjects compared to those who had never used the drug. Researchers also identified increased connectivity between certain regions of the brain in regular marijuana users compared with non-users.

So precisely what do these findings tell us in regard to pot use and health? Not much. Since the study design is not longitudinal, investigators cannot determine whether these differences are caused by subject’s cannabis use, whether these differences existed prior to subjects’ ever trying cannabis, or whether these differences persist when users’ cannabis consumption ceases.

Most importantly, investigators in this study failed to determine whether any of these differences are positively associated with any measurable adverse performance outcomes, such as cognitive performance or quality of life. It may be that these cannabis users are functioning in their daily lives in a manner that is indistinguishable from controls, in which case the imaging differences may hold little if any real-world significance. (In fact, one of the paper’s authors acknowledged, “[C]hronic users appear to be doing fine.”)

Don’t you love it when actors and neuroscientists scrap? There certainly was a good round of action last week when Ben Affleck and Sam Harris squared off on Real Time, Bill Maher’s HBO show. The dustup clearly touched a cultural nerve, sparking widespread coverage and commentary. Unfortunately, virtually everything that has been written and spoken about it missed the mark and added little to the important issues raised. (If you missed the Affleck-Harris blowup, view a clip here)

The problem with the aftermath is that most people seemed to have simply picked a side in lieu of listening and thinking. The result is that 99 percent of the commentary I’ve seen boil down to either, “Ben Affleck is an idiot”, or “Sam Harris is a bigot”. Few seem to have recognized that both men hold sensible positions on very important points and that the key problem that night was a failure to communicate, nothing new when religion is being discussed.

Affleck was right to be indignant. There really are many irrational bigots who slander and condemn every Muslim for the actions of some Muslims. He is justified in vigorously attacking such a stupid position and all who are shallow enough to promote it. But Affleck tripped up in thinking that Harris is one of these people. I am very familiar with Harris’s work and have never seen reason to suspect him of being a racist or bigot. And I pay close attention to such things, having written a book about the concept of race and the problem of racism. I'm confident that Sam Harris is not a racist. Here is one of the first things he said during his appearance on Real Time:

“We have been sold this meme of Islamophobia where every critique of the doctrine of Islam gets conflated with bigotry toward Muslims as people and that’s just intellectually ridiculous.”

Affleck failed to listen and immediately demonstrated Harris’s point by calling the critique of Islam “gross and racist”. This was, of course, “intellectually ridiculous”. I am very familiar with Harris’ work over the years and he does not attack “all Muslims”. In fact, he has consistently called for moderate, peaceful and sensible Muslims to push back against those who oppress, terrorize and kill in the name of Islam.