A recently-published study that examined opioid-related deaths in Colorado between 2000 and 2015 found a correlation between recreational marijuana use and a reduction in such deaths, suggesting that cannabis could be saving lives in that state. 
The authors wrote in the American Public Health Association that there was a 6.5% decline in deaths caused by opioids after Colorado legalized marijuana in 2014. This reversed a 14-year trend in rising deaths from opioids.
The researchers said:
“This reduction represents a reversal of the upward trend in opioid-related deaths in Colorado. Legalization of cannabis in Colorado was associated with short-term reductions in opioid-related deaths.” 
In the study, the researchers tried to correct for a change in Colorado’s prescription-drug-monitoring program that took place during the study period. That change required all opioid prescribers to register with the program in 2014, although they don’t have to use it. 
This is believed to be the first study to look at recreational rather than medical marijuana, comparing Colorado to Nevada, which allowed medical but not recreational cannabis during that period. The uniqueness of the study is part of why public health experts say that while the numbers look promising, they aren’t hearty enough to rely on when making policy decisions.
Executive Director of the Colorado Department of Public Health and Environment Dr. Larry Wolk said:
“It just hasn’t been in place long enough. Anything that does get published at this point should be considered preliminary data.” 
The authors point out that an association is not the same as cause-and-effect. They can’t say with certainty that pot legalization was directly responsible for reducing overdose deaths.
Some experts are unconvinced that marijuana alone is to thank for fewer opioid overdoses. One such skeptic is Robert Valuck of the Colorado Consortium for Prescription Drug Abuse Prevention, a state-led agency. 
“The whole thing is so convoluted that, with so many different things going on in the marketplace, it’s virtually impossible to assign cause and effect or credit and blame to any one thing.” 
Valuck also points out that heroin deaths in Colorado nearly doubled from 2011 to 2015, and there was a 1,562% increase in heroin confiscations by police in the state during that same time period.
Marijuana legalization could be an important tool in tackling America’s drug problem, but he’s not ready to call it a panacea.
“Everybody wants the answer now because we want to know if this is a good idea or not. But the truth is, we don’t have the answer, and it’s going to be a while until the jury comes back in.” 
The authors conclude:
“As additional data become available, research should replicate these analyses in other states with legal recreational cannabis.” 
The question is, how much proof that marijuana reduces opioid deaths do experts and policymakers need before it becomes a widely accepted fact and cannabis is legalized nationally?
A study published in the fall of 2016 showed that in states where medical marijuana is legal, fewer people use opioids.
In early 2017, the results of a survey of 250 people published in the International Journal of Drug Policy found that many people are turning away from deadly opioids and are turning to cannabis to ease their pain.
There is even evidence that suggests that cannabis may help people kick their addiction to hard drugs.
And let’s not forget that the drug industry takes marijuana seriously as a competing medicine. The drug company Insys, a maker of Fentanyl, poured tons of money and effort into fighting marijuana legalization in Arizona.