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Cannabis has been identified as a potential substitute for users of legal or illicit opioids, but a new Vancouver-based study shows the drug may also help reduce people’s cravings for another highly addictive substance: crack cocaine.Jim Mone/The Associated Press

Cannabis has been identified as a potential substitute for users of legal or illicit opioids, but a new Vancouver-based study shows the drug may also help reduce people's cravings for another highly addictive substance: crack cocaine.

Scientists at the BC Centre on Substance Use tracked 122 people who consumed crack in and around Vancouver's Downtown Eastside over a three-year period and found they reported using that drug less frequently when they opted to also consume cannabis.

"We're not saying that these results mean everyone will be able to smoke a joint and forget the fact that they are dependent on crack," said M.J. Milloy, an infectious-disease epidemiologist at the centre and senior author of the study. "What our findings do suggest is that cannabinoids might play a role in reducing the harms of crack use for some people.

"That's the next test: to what extent and for who?"

These results, published in the latest issue of the international peer-reviewed journal Addictive Behaviors, echo a smaller study of 25 crack users in Brazil that found just more than two-thirds of them were able to stop consuming that drug while using cannabis.

A recent global estimate pegs the number of people addicted to cocaine at about seven million, Dr. Milloy said, with many of them marginalized people smoking crack in cities across the Americas.

Brazil is struggling to cope with an epidemic that has made it the largest consumer of crack cocaine in the world. But the drug is also widely used by Canadians, Dr. Milloy said.

"Crack has not gone away and we have described in previous research how people using crack in a frequent high-intensity manner suffer from not only dependence, but other risks, in particular, HIV and hep C acquisition," Dr. Milloy said.

Addiction experts in Vancouver can offer those consuming heroin effective – and legal – substitutes such as suboxone and methadone, but there are no pharmaceutical therapies for people addicted to crack cocaine, Dr. Milloy said.

Cannabis was deemed less dangerous than tobacco in a 2010 study that ranked 20 legal and illegal drugs based on the dependence, social and physical harms they caused. The report, published in the British medical journal The Lancet, said both were considered far less dangerous to users and the general public than heroin, cocaine and alcohol.

As Ottawa gets set to legalize cannabis as early as next summer, addictions and public health experts such as Dr. Milloy have urged the federal government to consider the dangers – and potential benefits – that Canada's example of ending prohibition can offer the world.

One potential public-health benefit is more people may substitute cannabis for alcohol or opioids.

A recent study from the University of British Columbia and funded by licensed cannabis grower Tilray found more than half of the 271 medical-marijuana patients interviewed said they use cannabis to help them get off heavier prescription drugs, with the largest percentage saying pot acts as a substitute painkiller for opioids.

That research added to a small body of science that suggests patients are effectively using marijuana to replace opioids, a class of legal and illicit painkillers that has led to a crisis that last year killed hundreds of Canadians.

Last year, The Globe and Mail found fewer Canadian veterans have sought prescription opioids and tranquillizers in recent years, while at the same time, prescriptions for medical marijuana have skyrocketed.

It is not clear whether the two are related, but the trend echoes what researchers have found in U.S. states with medical-marijuana laws, where significant declines in opioid overdoses suggest that people may be substituting these oft-abused medicines with cannabis.

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