Study eyes weed legalization

Research claims little harm

BY JOHN INGOLD THE COLORADO SUN

Last year, a study came out showing that marijuana legalization in Colorado likely increased cannabis use among adults in the state.

Because of the novel methods the researchers used to examine the question, the study was perhaps the best answer to date on one of legalization’s biggest impacts. But it also left an even bigger question unanswered: Is it bad that more adults are consuming marijuana or doing so more frequently?

Now, in a follow-up study by the same team, using the same methods, the researchers have come to an answer: It doesn’t appear to be.

“At least from the psychological point of view,” said Stephanie Zellers, one of the researchers, “we really didn’t nd that the policies (on cannabis legalization) have a lot of negative in uence, which I think is important.”

Zellers recently graduated with a Ph.D. in psychology from the University of Minnesota, but she began her doctoral work at the University of Colorado before transferring when her thesis adviser changed jobs. She had originally been interested in neuroscience research, but the necessity of using live lab animals for the work was o -putting to her. And, in the Colorado-toMinnesota connection, she found a trove of data that could be used in never-before-tried ways.

The power of twins e data are from longitudinal studies of twins in Colorado or Minnesota. Researchers in both states followed the twins over long periods of time, collecting informa- tion about their behaviors, including their cannabis use. e survey information, then, creates an ideal scenario for study: It is thorough, it has built-in controls for variables like educational background or socioeconomic status, and it also accounts better than most for genetic di erences. at answer was interesting, but Zellers said it wasn’t really what the research team wanted to know.

On top of that, because Colorado has legalized marijuana and Minnesota hasn’t (at least so far) — and because some twins born in Minnesota moved to Colorado as adults and vice versa — the data provide an ideal opportunity to study the way in which a policy change made in Colorado a decade ago has in uenced people’s behavior ever since.

“ at twin component really allows us to rule out a lot of possible alternatives — maybe there were just cultural di erences, family differences, things like that,” Zellers said.

Zellers spoke with e Sun via videoconference from Finland, where she is pursuing postdoctoral research. (And, yes, she is missing sunshine this time of year.)

Homing in on the big question e original study, published last fall, simply asked whether twins living in legal-marijuana states use marijuana more than twins living in illegal states. And the answer is yes — about 20% more, according to the research.

“Really what people care about is: Is legalization harmful,” she said.

To answer that question, the team came up with 23 measures of what they call “psychological dysfunction.” is includes things like substance-use disorders but also nancial woes, mental health

Studies look into how marijuana legalization impacts other drug uses.