TL neuro

November 3, 2016

Thoughts on Proposition 64 to Legalize Recreational Marijuana in California

Filed under: Cannabis — mtaffe @ 10:41 am

I wrote a brief note on Facebook the other day to outline what I thought were several points that come up when people in the community ask me about the upcoming vote on recreational marijuana (link to ballotpedia summary of Prop 64). This was picked up in a post at Forbes by David Kroll (a handy summary video is here)

This piece was noticed by Sasha Foo at KUSI and she was kind enough to film a news segment which aired on 2 November, 2016. This links to the 6 pm broadcast version.

My Facebook remarks (with a few key links to data sources added):

I’m in California which will be voting on Proposition 64 which legalizes recreational marijuana. As many of my friends, neighbors and acquaintances are aware that I work in the substance-abuse fields of science, they have questions. So I thought I would put some of my usual responses/points down on a Fb post.

First, some background on my opinions. I work for you, the taxpayer of the US. This is because my work is funded by grants from the National Institutes of Health. Because these are primarily from the National Institute on Drug Abuse, my role is to investigate the effects of recreational drugs on the brain (and the rest of the body) with some attention paid to how this might affect the health of humans.

This is most emphatically not a policy role. I have no special expertise on public policy and my comments are not meant in that way. I do hope that science can be used to inform policy and, frankly, I wish that public policy across the board paid a lot more attention to facts and data. This is not to say, however, that I believe that the facts necessarily lead all interested people to the same *policy* decision. Because policy requires the weighing of factors and pitting positives and negatives of various kinds against each other.

As far as legalizing recreational marijuana goes, I do think that the epidemiological, human laboratory and animal laboratory data has some relevance to the Prop 64 issues. So, I’m going to list a few facts.

1) Marijuana is addictive. Full stop. The conditional probability of dependence is about 9% where like-to-like comparisons put cocaine and methamphetamine at 15%, heroin at 25-45% (data are terrible) and alcohol at 4%. Alcohol is a huge problem because 85%+ of people consume it at least annually. In contrast, less than 1% of people have ever tried heroin, 0.4% in the past year. Marijuana comes in at about 32% annual prevalence for ages 19-28. The scope of the addiction issue depends on how many people are using it, obviously. This will go up with legalization- but we don’t have any idea how much.

2) 5-6% of high-school seniors use Marijuana daily. Daily. That’s the US average. I don’t have numbers for California.

3) Marijuana addiction is as “real” as any other. Frequency of withdrawal symptoms and severity of those symptoms were compared between marijuana and tobacco smokers and the data were nearly indistinguishable. Most people are much more familiar with nicotine dependency (which is a higher rate, btw, probably 33%+) since it is more common, not embarrassing to discuss in public and is conventionally recognized. A lack of personal familiarity with the scope of withdrawal in the people who are marijuana dependent doesn’t mean that it doesn’t exist.

4) There is no such thing as “psychological” versus “physical” dependence since the brain is part of the body and the mind is the functioning of the brain. Keep in mind that people can be months to years out from their last use of any drug and still relapse severely. This is not being driven by the withdrawal symptoms that most everyone recognizes when they talk about “physical” dependence.

5) Marijuana acutely impairs cognitive and other behavioral functions.

6) Behavioral tolerance with chronic exposure is substantial. Blood levels of THC in animals or humans are a poorer proxy for impairment (versus other drugs) if you do not know anything about the prior exposure history.

7) THC is detectable in the body for a very long time compared with many other drugs of abuse. One study found detectable THC, or one of the main metabolites, for 30 days of in patient study (chronic users).

8) Trying to make specific predictions about an individual who uses marijuana from general findings (there is always a central tendency or average around which the distribution of data points or individual outcomes varies) is a fools’ errand. We can only predict general trends. Conversely, and this is important for your personal introspection, the evidence from one given data point or individual doesn’t tell us much that is informative about the average trend. The fact that it is your personal experience does not make it more valid.

Finally, there is much we simply don’t know. Any given scientific study or data set is limited by how it was generated. This doesn’t mean we throw up our hands and say it is all bunk or uninterpretable but it means one does have to think about it a bit.

I would invite you to read over the Prop 64 provisions. Personally, I see a fair bit of investment of the tax revenue in state sponsored activities to answer some of these issues better, to address some of the obvious concerns, etc. To me this is a positive. The extent to which this will happen, the extent to which actionable information will result, the extent to which activities intended to head off or ameliorate obvious negatives is, however, an unknown.


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