UC Davis Study Cherry-Picks Data For Youth Marijuana Legalization Fear


Maybe you saw the headline from Scientific American that read “Teens’ Views on Marijuana Change After Legalization“. Numerous media outlets repackaged the story, based on a study from University of California Davis.

It’s a perfect example of prohibition propaganda at work. Here’s the claim:

In Washington state, eighth graders’ perception of marijuana’s harmfulness fell by about 14 percent from before legalization (2010 to 2012) to afterward (2013 to 2015). Similarly, among 10th graders, the perception of harmfulness decreased about 16 percent.

Additionally, the proportion of kids reporting marijuana use in the previous month rose 2 percent among eighth graders and about 4 percent among 10th graders over that same period.

OK, so it’s not so much that teens’ views on marijuana changed after legalization, it’s that Washington teens’ views on marijuana changed. But wait, aren’t high school seniors also “teens”?

There were no significant changes in perceived marijuana harmfulness or use among 12th graders in Washington, however. The researchers speculate that older students may already have a fully formed opinion of marijuana.

OK, so, it’s not that Washington teens’ views on marijuana changed, so much as younger Washington teens’ views on marijuana changed following legalization in late 2012 that didn’t provide for the state’s first legal marijuana sale until July of 2014.

I understand that Colorado legalized marijuana in that same time frame. Did the younger teens in that state also find marijuana less harmful and increase their usage of it?

Additionally, the researchers didn’t see any significant before-and-after-legalization differences among students in Colorado. Possibly, they say, this might be because adolescents there were exposed to a robust medical marijuana industry before its recreational use was legalized.

Oh, I see. Since 2009, the existence of commercial medical marijuana transactions in Colorado already made those teens less fearful of marijuana and more likely to use it. Because Washington State’s commercial medical marijuana transactions since 2009 don’t count, since they were technically illegal and teens care about such things. Right.

LEGEND: Red text means one of the ten highest annual rates, green text means one of the ten lowest annual rates, boldface means lower than average rate. Any day now, that declining perception of harm from marijuana legalization is going to make them toke more.

I like to look up the data that is referred to in these kinds of stories, just to fact-check. According to the UC Davis researchers, they used data from the annual Monitoring the Future (MTF) study. The problem for me is that MTF doesn’t provide state-level data online; I don’t know how the UC Davis people got a hold of it.

However, there is another data set, the National Survey on Drug Use & Health (NSDUH), which is a larger survey that does provide me with state-level data to peruse. Unfortunately, I can’t break this data down by 8th, 10th, and 12th graders, but rather by the 12-17 age group. That shaves off the 18-year-olds who could be in MTF’s 12th graders and would likely perceive less harm and use more. However, it also adds in the 12-year-olds who haven’t reached 8th grade who would likely perceive more harm and use less.

Let’s see how that stacks up against the UC Davis hypothesis.

LEGEND: Currently-legal states are dark green, current medical marijuana states are light green, top ten increases are green text (#1 highlighted), top ten decreases are red text (#1 highlighted), boldface indicates above national average. Click for hi-res version.

At first glance, this seems to back up the UC Davis assertion about Washington State. It had the greatest decrease in harm perception (-42.15%) and its teen use shot up by over a quarter (+25.59%). The other state to legalize, Colorado, saw harm perception drop by over a quarter (-26.23%) and usage increase by over a quarter (+26.74%).

But look deeper at the only two other states to post greater usage increases than the two legalized states. Utah’s monthly usage increased by almost half (+47.28%) and North Dakota’s increased over a quarter (+27.27%). They didn’t legalize marijuana and they didn’t have active medical dispensaries, did they? In fact, since 2009, Utah has been consistently #1 and North Dakota consistently in the top ten for states with the greatest belief among teens that regular marijuana use is dangerous.


Other tidbits of information we can glean from the NSDUH numbers:

  • Six of the top 10 states with the greatest decrease in perception of harm were prohibition states;
  • Three of the top 10 states with the greatest decrease in perception of harm saw decreases in marijuana use;
  • Over half of the states (27) saw declines in teen marijuana use, despite every state’s declining perception of harm;
  • Massachusetts’ perception of harm has decreased the least, remaining virtually steady (-1.66%) since 2009, yet marijuana use decreased (-13.53%);
  • Minnesota (-21.65%), Tennessee (-20.34%), Ohio (-21.23%), and Illinois (-22.07%) are right near the US average (-21.35%) for the decline in perception of harm and none of those states had medical marijuana in this time frame, yet Ohio (-20.63%) and Illinois (-10.36%) use declined and Minnesota (+10.84%) and Tennessee (+6.74%) use increased;
  • California’s had the most robust medical marijuana market, pre-dating Colorado and Washington by a decade, yet while California’s perception of harm dropped almost a quarter (-23.26%), its usage remained relatively stable (+1.63%);
  • Iowa saw the greatest decrease in monthly use, dropping over a quarter (-25.50%), yet its decline in perception of harm (-21.49%) ranks in the middle of the pack and almost matched the US average;
  • Two of the top 10 states for the least decrease in perception of harm saw increases in marijuana use.

Here’s the bottom line: when we’ve spent decades trying to scare kids into thinking smoking pot will scramble their brains and lead straight to heroin, of course they’re going to perceive of regular marijuana use as less harmful the more they’re exposed to realistic information about it. As teens see more adults using it legally without health and legal repercussions, of course they’re going to fear regular marijuana use less. Using teens’ realization that they’ve been fed reefer madness for drug education is no way to gauge whether they’ll use marijuana.

Isn’t it remarkable how far some public policy experts will stretch to find any little nugget of predictive harm about marijuana legalization, while ignoring the correlation between liberalizing marijuana laws and the lowest levels of drug, alcohol, and cigarette use by teens ever recorded?

Leave A Reply

Your email address will not be published.