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 In recent years, many advocates for legalizing marijuana - including
some doctors and public health officials - have cited a pivotal 2014
study that found lower rates of fatal opioid overdoses from 1999 to
2010 in the states that legalized medical marijuana.
For the current study, published in the Proceedings of the National
Academy of Sciences, researchers used similar methods to take
another look at the same period examined in the 2014 study and
extend the analysis through 2017, to include many states that only
recently legalized medical marijuana.
The new study found a similar result for the same period covered in
that 2014 study: about a 21 percent decrease in opioid overdose
deaths for every 100,000 people in the population when states
legalized medical marijuana.
But when the new study looked over more time - from 1999 to 2017 -
they found an almost 23 percent increase in opioid overdose deaths
in states with medical marijuana laws.
"With the benefit of a longer time span ... we conclude that medical
cannabis laws do not seem to have reduced opioid overdose mortality
at the population level," said lead study author Chelsea Shover of
Stanford University School of Medicine in California.
Like the 2014 study, the new analysis can't show whether people are
using marijuana instead of opioids for pain relief or recreation,
Shover said by email. And these studies also weren't designed to
determine the safety or effectiveness of medical marijuana for any
specific health issues.
The current study didn't find a difference in opioid deaths
associated with legalized marijuana based on how permissive or
restrictive state laws might be, or whether states allowed only
medical pot or also permitted recreational use.
California became the first state to legalize medical marijuana in
1996. Today 47 states permit some version of medical pot.
It's possible that the connection between marijuana laws and opioid
overdose deaths has shifted over time due at least in part to
differences in the characteristics of the states that did this years
ago and states that did this only recently, the study authors note.
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"States that legalized medical cannabis early formed a group that
was pretty different from the rest of the U.S.," Shover said.
The first study was comparing a group of 13 mostly western,
politically liberal states to the rest of the country, and the rest
of the country also happened to be where the opioid overdose crisis
was growing," Shover added.
"I think that shared characteristics between those 13 states -
things like less incarceration of people using drugs, more
availability of treatment for opioid use disorder, and more
availability of the overdose reversal drug naloxone - explain the
association they found," Shover added.
Now that almost every state has passed some version of a medical
marijuana law, "you get to see how it plays out in a more
representative group," Shover said.
Still, the results were a surprise to Brendan Saloner, a co-author
of the 2014 study and a researcher at Johns Hopkins Bloomberg School
of Public Health in Baltimore.
"I was not expecting this finding, but I think that it could
plausibly be explained by the changing nature of the opioid crisis,"
Saloner, who wasn't involved in the current study, said by email.
"Specifically, heroin and fentanyl have been involved in a lot more
overdose deaths - including deaths that also involve prescription
opioids -- and that could reduce the protective effect of medical
cannabis," Saloner said.
"Second, the states implementing medical cannabis laws, and the way
these laws have been implemented, has been changing over time, and
it may be that they are getting less effective at reducing harmful
opioid use," Saloner added.
SOURCE: http://bit.ly/2WwZtvE Proceedings of the National Academy of
Sciences of the USA, online June 10, 2019.
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