To pot or not?

Dear Doctor Ninja,

I’m an active dude in his early 40’s in Canada where cannabis was just legalized. I’ve never used pot before. I’ve been hearing how CBD oils are great for better sleep, and less inflammation. I’m pretty interested in both of these benefits especially as I get older. But there’s a science reported on a website that says my brain could become less connected to itself if I use it (website included). What should I do?

G. Anja

The science you’re worried about is this: Zimmermann K et al. Emotional regulation deficits in regular marijuana users. Human Brain Mapping .Aug;38(8):4270-4279. doi: 10.1002/hbm.23671, 2017.

There are two answers (and one bonus answer) to this question, but all lead to the same answer.

This study picked 23 men who use marijuana, and 20 men who didn’t use marijuana.

Answer 1:

CBD oil is usually derived from hemp, and the main active ingredient is cannabidiol (hence CBD). The main active ingredient in marijuana is THC (tetrahydrocannabinol).

So before we move any further, this is a problem.

Suppose you have a friend who says, “We should go to this party. Because ballroom dancers love it and there are rave reviews from ballroom dancers online.”

The first question you should ask your friend is, “Are we close enough to ballroom dancers that we should consider ourselves essentially ballroom dancers and go to this party?”

If you’re a ballroom dancer, you should go. That sounds like a lot of fun.

If you’re not a ballroom dancer but you want to be a ballroom dancer, you should go. That sounds like a lot of fun.

If you’re not a ballroom dancer and you don’t want to be a ballroom dancer, then you have to decide whether you care enough about what ballroom dancers think about this party to commit your night to it. Chances are, if you’re not a ballroom dancer and don’t have aspirations to become one, the opinions of ballroom dancers are not terribly useful in making this decision.

The first question you should be asking about this science is, “Is CBD close enough to THC that I could consider them the same thing.” The answer at this point in time, seems to be “No.”

You can stop reading here if you want.

Answer 2:

Let’s pretend that you asked a question about THC oil, since that is going to be legal in Canada (it’s not legal to sell yet.) so that we can get on an apples-to-apples page.

In order to be considered a marijuana user in this study, you had use marijuana at least 3 days a week for the past year, and you had to have used it at least 200 times in your lifetime. You cannot have used any other illicit substance more than 50 times in your life or in the last 28 days before testing. You had to have not used marijuana for 48 hours before testing.

The authors did not define what was meant by “marijuana use”.

If you ask someone about their use of cookies, where use is eating and not smearing cookies on their skin, I think we would all agree that eating one cookie is a use of cookies. But we all know that there are people who eat just one cookie (it’s real, they DO exist) and then there are the rest of us who think of “one cookie” as a sleeve of cookies. You would never trust a diet study to help you decide about eating cookies that asked about cookie usage without quantifying what cookie usage meant.

So why would you trust a brain study to help you make a decision about THC use that asks about marijuana use without quantifying what marijuana use means?

Bonus Answer:

So far, we STILL can’t use this as a trusted reason on which a decision could be based.

So, let’s pretend that the authors DID quantify marijuana use, and that it magically fell in the range that you are thinking of using it.

The authors showed subjects either neutral or negative (i.e. disturbing) images while in an MRI machine. The asked subjects to rate how negative they felt when shown either neutral images, or disturbing images. On some disturbing images, subjects were asked to try to distance themselves emotionally from the disturbing image so that they felt less disturbed by them.

The authors noted that globally, when they considered all the ways you could compare the different groups and image conditions, that there was evidence to suggest that there was a difference in the whole group’s (both marijuana users and non-marijuana users together) negativity rating between neutral images and disturbing ones. They also found that there was evidence to suggest that there was a difference in negativity rating between disturbing images without the request to distance from the image, and disturbing images WITH the request to distance, again in the whole group.

There was no evidence to suggest that marijuana user were different from non-marijuana users.

The main conclusion is attempted to be justified by a test performed after the global test concluded that there was no effect of group (marijuana or no marijuana) which showed a statistically significant effect. Why the authors insisted on performing a test that was not statistically warranted is unknown, but it would be considered inappropriate.

This is the linchpin of this science. In order to state that differences in brain connectivity are related to a decreased ability to distance yourself from negative images, you have to prove that marijuana users are worse at distancing themselves from non-marijuana users. If you can’t show this, then no one cares what the differences are in brain activity. The authors depend on an inappropriate statistical finding to tie the two things together. That makes this knowledge unreliable at best. But in case Answer 3 doesn’t stack up, the TL:DR is the same because of Answers 1 and 2.


I’m not saying that you should or you shouldn’t use CBD oils. That’s a choice that goes beyond whether your brain gets less connected to itself or not. But if the story the science you’re worried about doesn’t study the thing you’re using, doesn’t tell you how much is considered using the thing, and has a dubious statistical result, then it’s not a science that can help you make this decision, regardless of what that story says.

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