Marijuana Use, Abuse and Dependence Increased Over the Past Decade

Oct 23 2015 Published by under Cannabis, Drug Abuse Science

A new paper from Hasin and colleagues at JAMA Psychiatry reviews data:

from NESARC and from the National Institute on Alcohol Abuse and Alcoholism
2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions–III (NESARC-III), a survey of 36,309 new participants.
...
The NESARC field procedureswere similar to those in NESARC-III.

There are really three key observations, although the tables also break down the findings by sex, age, race/ethnicity, education level, etc.

First, past year use of marijuana went from 4.1% to 9.5% of the sampled populations. Interesting, but hey, could just be more people feeling free to try it out, right?

Second finding looked at prevalence of meeting DSM-IV criteria for a Marijuana Use Disorder (including Abuse and Dependence subcategories) in the past year. This measure went from 1.5% to 2.9% of the population.

The third finding is that if you condition only upon those individuals who have tried marijuana at least once in the past year, the rate of a Marijuana Use Disorder went from 35.6% to 30.6%.

This is all relevant to a few themes we've discussed before on the blog.

I don't see how you can view these data other than in a context of growing liberalization of medical marijuana laws and availability of marijuana. This refutes the occasional position struck by the pot fans that changes in legal status and attitude won't change use rates because everyone who wants to smoke marijuana already does. Clearly the US population undergoes significant changes in exposure to marijuana. In this case only over a decade.

My position has also been that, in general, as you increase the number of people who are exposed to a given drug you are going to see an increase in problems related to that drug. In the absence of other information, we must start our estimate of that rate from what we observe at a given time. The first two numbers in the study confirm this. As use rates increased, so did rates of meeting criteria for DSM-IV diagnosis of a MUD.

The conditional probability measure also addresses this phenomenon, perhaps in an even better way. I have mentioned before that it is really hard to assess conditional probability of dependence between drugs that feature significant base-rate exposure differences. You can't help but assume there is going to be a curve whereby the more democratic the exposure, the larger will be the occasional user population. That is, I assume some sort of nonlinearity is going to occur against the general estimation I mention above. I presume the lower the incidence of exposure to a given drug, perhaps the higher the conditional probability of dependence and the higher the incidence of exposure, the lower the conditional probability.

In this case, I'd say the change in conditional probability is not that significant. Something around a third of those who smoke marijuana in a given year are meeting criteria for a MUD across a doubling of the incidence of exposure. The curve is still pretty linear although I assume we will be getting another jump in a decade and can see how this curve shapes up.

This estimate of a MUD is really high to my eye, no doubt because it includes abuse and dependence together. Perhaps the data I usually think about (7-9% dependence rate) references dependence without abuse...I have to go check on that. In case you are wondering, the difference really boils down to symptoms of tolerance (diminished effect at same dose, increasing dose to get desired effect) and withdrawal, as well as some indicators of uncontrolled use relative to a person's intentions.

Now interestingly the authors reference another similar study (NSDUH) that didn't find an increase in prevalence that was so large- only 12% reported by Pacek et al, 2015. The present authors suggest more detailed questioning in the NESARC approach may explain the difference.

9 responses so far

  • boba says:

    The only question I have about this science is: Can the rest of the field repeat it? Namely, is it something that can be verified by other investigators. The last paragraph shows that there is a substantial disagreement between studies, and the hand-waving that these authors offer doesn't appear to be convincing.

  • Philapodia says:

    Yer harshing my buzz with your "numbers", man!

  • drugmonkey says:

    Why is it "not convincing", Boba?

  • boba says:

    "The present authors suggest more detailed questioning in the NESARC approach may explain the difference."
    The claim is that use increased by X amount. A comparable study claims that use increased by Y amount. Please inform this skeptical reader, what possible question could be more detailed than:

    Have you used marijuana in the past year?

    Either the earlier study was wrong as to the amount of usage in prior years, which means the increase is not as great as this study claims, or the studies themselves are flawed in that they cannot ascertain baseline data.

    Hand-waving, the bread and butter of these studies.

  • drugmonkey says:

    Please inform this skeptical reader, what possible question could be more detailed than:

    Have you used marijuana in the past year?

    In survey methodology there are many approaches. One is time-line follow-back. You can also imagine that the context and setting makes people more or less honest about their behavior. Asking multiple times over the course of a survey can identify differences, etc. So that's why I asked you. I was wondering if you had an informed opinion about the differences in methodology or any particular reason to be skeptical of the authors' assertions. I assume from your comment that this is a "no".

    Given this, how would you know which particular outcome is "not convincing"? how do you know the 12% increase isn't the bogus finding and that the present paper isn't the better estimate?

    The authors did cite three other data sets which imply increases in cannabis use higher than 12% as well- MUD in vets 2002-2009, emergency dept visits for cannabis 2004-2011 and fatal car crashes 1999-2010.

    Hand-waving, the bread and butter of these studies.

    What are "these" studies? Any epidemiological investigation on any topic? Any study at all that doesn't come to the exact same conclusion as related literature? Or are you asserting the problem is with pot epidemiology in particular?

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  • Dean Austin says:

    Well, you've convinced me. The only thing left to do is re-criminalize marijuana in the jurisdictions where it has decriminalized and start locking people up for possession again everywhere.

  • anon says:

    "This refutes the occasional position struck by the pot fans that changes in legal status and attitude won't change use rates because everyone who wants to smoke marijuana already does."

    I have always thought this is the most ridiculous "defense" of pot I have ever heard. Partly because *I* would personally indulge on occasion if it were not illegal where I am. Likewise, if alcohol was illegal, I probably would not drink - or I would drink a LOT less (while possibly campaigning to end prohibition or at least supporting candidates that support ending prohibition).

    I mean... they are essentially arguing that there are NO PEOPLE who are deterred from doing illegal shit because it is illegal. It's just patently absurd.

  • drugmonkey says:

    Of course it is. But when you have chosen a lifestyle entirely surrounded by pot heads you can see where they might be a little constrained in viewpoint.

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