Researchers discuss effects of cannabis use

[00:00:00] Host Amber Smith: Upstate Medical University in Syracuse, New York invites you to be "The Informed Patient" with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith. The use of cannabis, or marijuana, has rapidly increased as it becomes legal in more and more states. Does its use impact cognitive function? Public health and geriatrics researchers at Upstate examined whether cannabis consumption is associated with subjective cognitive decline, and they're here to tell us about their findings. Roger Wong is an assistant professor of public health and preventive medicine at Upstate, and Zhi Chen is a graduate student in Upstate's Master of Public Health program. Welcome to "The Informed Patient," both of you.

[00:00:46] Roger Wong, PhD: Thank you for having us.

[00:00:47] Host Amber Smith: So, Dr. Wong, would you please tell us about this study? Did the data come from people here in Central New York?

[00:00:54] Roger Wong, PhD: Sure. I'm happy to talk about the study. And actually, before we begin, Zhi and I haven't talked since we published this paper, but I just want to really congratulate Zhi first. This paper was her final project for my advanced biostatistics course I teach for the Master of Public Health program at Upstate. And it was a fantastic paper. She is the first author on it. I submitted it three months ago. It got accepted in one month, which is really impressive for a master of public health student. So I just really want to formally congratulate Zhi for all the hard work she put into this project.

So, Amber, your question was about the people in the study. So we analyzed data from, it's B-R-F-S-S, otherwise known as "the Brif-iss." The BRFSS, it stands for the Behavioral Risk Factor Surveillance System. It is a data set that is administered by the CDC, which is the Centers for Disease Control and Prevention. It's a really nice data set because, like, anyone could literally just go to the BRFSS CDC website and just download it without an account or anything. So it's really nice, if anyone wants to ever try to replicate what we found here.

They have started collecting this data in 1984, and it's a very, very long questionnaire, has a variety of different questions about health risk factors, and they collect data from adults 18 years and older in all the United States and also DC and a few territories as well.

And every year they ask questions to around half million people. So it's a quite a large data set. The questions about cognition, they're only asked to adults age 45 years and older. So as a result, even though every year they have around half million people in this data set, we then restrict it to only people that answered these cognition questions. So as a result, we have a sample size of around 5,000 people. But we do something in statistics called weighting, where the results are adjusted to be more generalizable to the whole US population. So it's actually representing about 500,000 people, the results we're talking about today.

[00:03:10] Host Amber Smith: Well, Zhi, can you tell us what their ages were, and how you set it up?

[00:03:15] Zhi Chen: We included adults 45 years and older, and that's because in this survey data, our outcome variable subjective cognitive decline was only assessed among those above this age threshold. And actually within our study population, nearly half of the respondents were 65 years and older.

[00:03:37] Host Amber Smith: So were they all cannabis users, or did you have some that did not use cannabis?

[00:03:43] Zhi Chen: Yeah, we have a reference group. So about 92.5 % of the respondents in our study population had not used cannabis in the last 30 days. And in our analysis, we compared cannabis users to this group of none users.

[00:04:03] Host Amber Smith: So you looked at subjective cognitive decline. Dr. Wong, is that if a person just feels like they're more confused or having memory problems?

[00:04:14] Roger Wong, PhD: Yes, the way that it's asked in the BRFSS is in the last 12 months, whether or not they've had any sort of confusion or memory loss that's been getting worse. I think it's a really great measure of, typically an early sign of something known as mild cognitive impairment.

And there's a lot of research that have shown that subjective cognitive decline -- which I think Zhi and I, we might abbreviate to SCD -- SCD has been shown to increase our risk for dementia by about two times. And currently there is no cure for dementia, and there's no way that we can effectively prevent it. So that's why I think SCD is a really great measure because we want to figure out how we can kind of reduce and prevent our risk for cognitive decline before we develop dementia later in life.

One question I often get about subjective cognitive decline in the BRFSS is that, how come they couldn't really measure cognitive decline objectively, which I think is a fair point. But if you remember, this is about half a million people in this data set. There are so many questions, and it's not realistic to administer a full length objective cognitive decline module. So as a result, the best we can do is just ask them if they have any sort of confusion or memory loss. And oftentimes this is a pretty reliable measure too.

[00:05:40] Host Amber Smith: Well, you looked at the reason for cannabis consumption, the frequency, and the method. Zhi, can you explain the variations in each of those? What were the various reasons for cannabis consumption?

[00:05:54] Zhi Chen: In the survey, the general question on cannabis use focused on the use within the last 30 days. Then, for the reasons of cannabis use, there were those who used for medical reasons, and then non-medical purposes, and a combination of both.

[00:06:12] Host Amber Smith: What was the range of frequencies?

[00:06:15] Zhi Chen: The frequency of use, the question was, in the last 30 days how many days did they use cannabis? So the responses ranged from zero to 30 days.

[00:06:26] Host Amber Smith: I see. And then, what were the different methods that you looked at?

[00:06:31] Zhi Chen: The answers to the methods of consumption included smoke, eat, drink, vaporize and dab. And smoke was the most common method. And there were also a very few responses that fell into the "other" category because the number was so small, it was excluded from the analysis.

[00:06:52] Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host, Amber Smith, and I'm talking about the effect of cannabis on cognition with Roger Wong, who's an assistant professor of public health and preventive medicine at Upstate, and masters of public health graduate student Zhi Chen

Let's talk about your findings. Do cannabis users see more, or less, cognitive decline, Dr. Wong?

[00:07:18] Roger Wong, PhD:

So starting with the reason for why they're using cannabis, we found that compared to people that do not use cannabis, those that use cannabis for non-medical reasons -- so this includes recreationally -- they have about a 96% significantly lower odds of having subjective cognitive decline.

I've been getting quite a few questions from the lay public about,how does the body recognize the difference between if you're using cannabis medically or non-medically, which I think is a fair point. And obviously we didn't write this paper for the lay public. It's more for the scientific community.

I want to kind of emphasize, and what we talk about in the paper, is that medical cannabis, it typically has higher concentrations of a compound called CBD. In comparison, nonmedical cannabis has higher concentrations of a compound called THC. So we found in our paper that non-medical cannabis use has a lower odds of SCD later in life. And we write in the paper, we think the mechanism is because typically non-medical has THC, and a lot of people use non-medical THC to help with sleep and also stress relief.

And I might be biased because I'm a dementia researcher, but there's a lot of people that come up to me and tell me that they use cannabis to help them fall asleep at night. And last year I came on "HealthLink on Air," and we talked about how in one of my major papers, those with sleep disturbances, they had a higher risk for dementia. So that's kind of the mechanism we talked about in the paper that Zhi and I wrote.

[00:08:56] Host Amber Smith: Interesting. So, does the frequency of use affect whether someone feels like they've got cognitive decline or not?

[00:09:06] Zhi Chen: The frequency of use was not associated with SCD. This may come as a little bit of a surprise, because some previous studies, which often focus on the frequency of use, suggested a negative relationship between cannabis use and cognitive performance.

That kind of highlights the key component of our study, which is to account for not only the frequency, but also the reasons and methods of consumption. And one more thing to note is that some relevant study looking into different age groups have shown that younger individuals might experience more pronounced cognitive effects from cannabis use, while the impact on older adults may be less significant. And that's really relevant to our research because we focused on middle aged and older adults.

[00:10:03] Host Amber Smith: Did you find a big difference in the method of ingestion?

[00:10:07] Zhi Chen: Similar to the frequency of use, we found the method of consumption was not associated with SCD, either.

We thought how cannabis is consumed is critical to be considered because generally, smoking delivers more immediate effects, while edibles and drinks have a delayed onset of effects, which may lead to higher consumption. These differences could influence cannabis impact on cognitive abilities. It's also important to note that many users don't stick to just one way of consumption. Although smoking is the most common, I think about one third of those who smoke it also engage in other methods such as dab, or edibles. This is one limitation we have in this data.

[00:10:56] Host Amber Smith: So people who use cannabis recreationally actually had less, or felt like they had less of a cognitive decline. Do I understand that? That's right. So did this surprise you?

[00:11:10] Roger Wong, PhD: It surprised me. I'm not sure about you, Zhi. And Zhi, I think she kind of hinted at this. The reason why I think this study is such a huge contribution to the literature is because -- Zhi, she was talking about earlier how other studies have found more frequent use of cannabis is linked to worse cognition -- and the reason why our study is so different is 1. We looked at multiple different dimensions of cannabis use, not just frequency, but why they're using it, how they're using it. I don't think such a study has been done before. So you really need to account for those other cannabis dimensions when you're doing this sort of analysis. So that's one part that I think is different.

And I think, Amber, you kind of hinted at the other contribution we made as well. For the BRFSS, this data set, the cannabis questions were only asked to those that use cannabis. And I think that's the case for others that also analyze something similar to this data. They only look at people that use cannabis. So Zhi and I, we were talking about this project in the advanced biostats course. And then, actually, there was another MPH student who's now doing his residency. He brought up the idea of maybe we should have put back the people that don't use cannabis. I'm like, why didn't we think about that? So, the coding was a little bit more difficult. They were trying to bring back the non-cannabis users so that we can have them more as, like, kind of the reference group that we could compare to. So that's another piece where I think the study results are a little bit different.

[00:12:42] Host Amber Smith: So let me ask you this: If people are using cannabis, might that cloud their judgment, so they can't really give you a good quality, subjective assessment?

[00:12:53] Roger Wong, PhD: That is another question I've been getting from the lay people. I mean, like, they're not stoned all the time. We're on the telephone asking them all these questions. So, I mean, hopefully they're lucid enough. I think most of us like know in the last year if we've had any, like, major episodes of memory loss. So that's why I think it's still a reliable measure, but I mean, I think it's maybe a fair point. It's like, are they stoned when they're having these issues?

[00:13:20] Host Amber Smith: Are there other factors that weren't part of your study that might be influencing the findings?

[00:13:27] Roger Wong, PhD: Yes, and my apologies if we didn't mention this, but it's either for the cognitive decline module cognition question or the cannabis question, but one of them, it's only asked to a limited number of eligibility. So, it's only 14 US states and also Washington DC that's included for analysis in this study. There's some issues with that because there's currently 38 states in the US that have legalized cannabis for medical reasons, and then there's also 24 states that have legalized cannabis for non-medical reasons. So there's really varying laws in the US right now on medical and non-medical use for cannabis. So I think that complicates the whole analysis, and we didn't really account for those legal issues.

[00:14:14] Host Amber Smith: Well, what additional research do you think should be done on the use of cannabis and cognitive function?

[00:14:20] Roger Wong, PhD: I think one important takeaway that I want to mention is that I don't want people thinking, " I just listened to this podcast, and they're saying that I should like smoke a joint tonight to protect my cognition." That's not what we're saying. The important point I want to make is first, there might be some evidence that cannabis might be protected for our cognitive health later on. But I think more importantly than that, we also -- and my apologies, we also didn't mention this -- we only looked at one year of the BRFSS dataset. So this is the 2021 BRFSS. And the reason why we only looked at one year is because the three cannabis questions, they're only asked in this one year. So that's the reason why we couldn't really combine all the different years together because those cannabis questions were not asked.

So I think this warrants some future research into more long-term, longitudinally, what is the association between cannabis use and cognition? And I think that would be really beneficial for the scientific community. But I think right now, realistically, that might not be possible because currently cannabis is classified as a Schedule I drug. So that means it's also illegal, federally, as well.

[00:15:33] Host Amber Smith: Well, it's very interesting, and I do appreciate both of you making time for this interview.

[00:15:38] Roger Wong, PhD: Yes. Thank you for having us, Amber.

[00:15:41] Zhi Chen: Thank you.

[00:15:42] Host Amber Smith: My guests have been Roger Wong, an assistant professor of public health and preventive medicine at Upstate, and Zhi Chen, a graduate student in public health at Upstate. "The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York, and produced by Jim Howe. Find our archive of previous episodes at upstate.edu/informed. If you enjoyed this episode, please tell a friend to listen too. And you can rate and review "The Informed Patient" podcast on Spotify, Apple Podcasts, YouTube, or wherever you tune in. This is your host, Amber Smith, thanking you for listening.