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Study Links Medical Marijuana Laws With Drop in Traffic Deaths


A new study finds medical marijuana laws are associated with a reduction in traffic deaths. The most likely reason for the decrease is that some people in states with the laws use marijuana instead of alcohol, the researchers say. They note that alcohol is more deadly than marijuana when combined with driving, according to The Wall Street Journal.

The researchers examined data from the National Highway Traffic Safety Administration before and after passage of medical marijuana laws in 16 states. They found a nearly 9 percent decrease in overall traffic deaths. The decline was caused almost entirely by a decrease in alcohol-related traffic deaths.

In most states with medical marijuana laws, the researchers saw an increase in marijuana consumption in addition to prescription uses among people over 18, but not among minors. Those states also experienced a small drop in alcohol consumption. The researchers conclude that marijuana is being used as a partial replacement for alcohol.

The researchers point out that people who use marijuana may be more likely to do so in private, while alcohol is often consumed in restaurants and bars, which often leads to drinking and driving. They also say people who are drunk tend to be less aware of their intoxication than people who are high on marijuana.

The researchers’ findings appear in a working paper for the Institute for the Study of Labor.

13 Responses to this article

  1. compassion / December 12, 2011 at 4:16 pm

    Politics and money, not facts and science, drive the war on Mj.

  2. Carlos / December 3, 2011 at 4:47 pm

    I AM NOT GOING TO MAKE ALL KINDS OF CONCLUTIONS BASED ON ONE STUDY. We have this tendency of “conformational bias”(is everywhere) Seems to be one of the component in treatment failure, medical errors and a host of cognitive errors afflicting the clinical practitioner.

    People whether we like it or not the psychological allied professions is a science (is not as artistic as we like to claim; if you think it is an art, prove your claim) we continuo to major ignored. Most of us haven’t read a journal since we left college.

  3. Benny / December 2, 2011 at 12:39 pm

    This was not a study published in a peer-reviewed journal, but rather a “discussion paper”. I find it interesting that the high cost of gasoline in the selected states was not a consideration.

  4. Avatar of Martha Johns
    Martha Johns / December 2, 2011 at 6:59 am

    I never cease to be amazed at the number of so called researchers who think a correlation between two things indicates “causality”. they must have skipped statistics 101. There are many reasons that traffic deaths due to alcohol have gone down… Not the least of which is better enforcement of underage drinking laws, the recession reducing unnecessary trips and many other factors including improved vehicle safety.

  5. meltee / December 1, 2011 at 8:35 pm

    Three comments:
    1)Its only correlational, but empires have been built on correlational data.
    2)I wonder what prompted them to look at the data that way?
    3)Hypothetically, if studies showed that legalizing medical use, or totally legalizing adult use of MJ, resulted in reduced overall health harms, (leaving aside the issue of any potential medical benefits for some disease conditions) would the prevention policy folks still oppose legalization?

  6. Marco / December 1, 2011 at 2:15 pm

    i am in awe at the recent articles pushing the use of marijuana as a “medicine”. I did 12 years of Federal time for smuggling Marijuana in the 80′s, fougfht tooth and nail about the harmless effects that marijuana has in comparison to alcohol and other drugs; but in reality I am a strong opponent to any legalizing of marijuana. I went from a straight A’ student in High school. to a self medicating, procrastinator when turned on to marijuana. Mind you I realize Not everyone has the same side effects,like severe munchies, procrastination, (a sort of don’t give a rats !#8&() attitude about life, but if it were up to me. I’d call this whole movement what it really is, a way to get high, for whatever reason at the expenses of calling it a medicine, Give me a break. Furthermore, the federal sentencing guidleines convert most of all drug charges to a marijuana equivalent at sentecing ( ex: 1- Kilo of cocaine = 1,ooo lbs of marijuana) therefore imagine the outcry from non violent offenders if marijuana was legalized, the Govt would have to change the way they sentence federal inmates under new guideline tables. I don’t think that will happen. The old draconian stance upon marijuana users is embarrasing if not outright disgusting by law enforcement, who still break down doors for the weed. But there has to be a definite adult stance that can remedy these laws without trying to push this whole medicinal nonesense on all of us. Me included!

  7. Avatar of concerned parent
    concerned parent / December 1, 2011 at 12:42 pm

    It may be a short term decrease as people use marijuana at home not, but how long will that last? The more accepted medical use and non-medical use of marijuana becomes, the more people will drive to gathering locations for a communal high – sharing the “good times”. It would be best if anyone getting a medical marijuana perscription also surrender their driver’s license. There are other drugs which when perscribed prohibit the use of a motor vihicle, we should take them all seriously, and provide state ID’s that indicate the individual takes these type medications. It will make our roads even safer.

  8. Avatar of pfroehlich2004
    pfroehlich2004 / December 2, 2011 at 11:14 am

    The federal government actually publishes traffic fatality data for all 50 states and the District of Columbia.

    Traffic fatality rates have fallen in every state since 1994, however, on average, they have fallen more in states with medical marijuana laws.

    The 9 states which legalized medical marijuana by 2004 (AK,CA,CO,ME,MT,NV,OR,VT,WA) improved in ranking relative to other states by an average of 0.55 places. So, it would seem that the decrease in fatalities is not a short-term phenomenon. This was also the conclusion of the study referenced in the article.

    (Link to study)
    (Traffic fatality data):

  9. pfroehlich2004 / December 2, 2011 at 1:15 pm

    Why then have alcohol-related traffic deaths declined MORE in states with medical marijuana programs than those without them?

    Do medical marijuana states have stronger enforcement of drinking age laws than non-mmj states? Has the recession caused a greater reduction in unnecessary driving trips in states with medical mj laws than in those without them?

    There actually is a way to determine whether a given correlation indicates a causal relationship. It’s called controlling for extraneous variables and this is what the researchers did in this study. They compared traffic fatality data from mmj states with neighboring non-mmj states and controlled for variables such as unemployment rate, per capita income, and local speed limits. This is sound scientific methodology.

    Perhaps you should try reading the study.

  10. billinsandiego / December 2, 2011 at 4:58 pm

    Agree. This seems too much like a “post hoc” argument. Has there been a relational decrease in on-sale alcohol purchases? That would better support the hypothesis. Although I am not an anti-medical marijuana person, I am a research questioner – there are too many other factors to consider.

  11. pfroehlich2004 / December 2, 2011 at 1:28 pm

    Probably because of the lack of significant variation.

    Avg. gas prices in mmj states and non-mmj neighbors examined in the study:

    RI (mmj): $3.39/g
    CT (non): $3.56/g
    MA (non): $3.32/g

    VT (mmj): $3.40/g
    NH (non): $3.26/g
    NY (non): $3.57/g

  12. Richard P Steeb / December 3, 2011 at 12:26 am

    Google THC+SDLP and perhaps you’ll find the abundance of data interesting…

  13. pfroehlich2004 / December 2, 2011 at 11:26 pm

    Did you read the study?

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