People who use drugs may use cannabis and drug cocktails as a form of harm reduction

Maria Eugenia Socias at HR17. Photo by Liz Highleyman,
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People who use drugs have come up with innovative strategies that help them reduce harm, including using marijuana to decrease crack use and mixing heroin with methamphetamine to moderate the effects of meth or prolong the duration of heroin's effects, according to presentations at the 25th International Harm Reduction Conference (HR17) last week in Montréal.

Cannabis and crack

Unlike opioids, there is no medically recognised pharmacological therapy for problematic crack cocaine use. Prior research has shown that cannabis and its components, known as cannabinoids, can help people reduce their use of opioids. Emerging evidence, including data from animal studies, suggests cannabis may also reduce cravings for crack, possible by modulating reward pathways in the brain.

Maria Eugenia Socias of the British Columbia Centre on Substance Use presented findings from a study of harm reduction practices among people who use crack in Vancouver. The results were also published in the September 2017 edition of the journal Addictive Behaviors.

"We found that intentional cannabis use preceded declines in crack use among crack cocaine users who pursued self-medication with cannabis," Socias said.


harm reduction

Harm reduction is a set of practical strategies and ideas aimed at reducing negative consequences associated with drug use (including safer use, managed use and abstinence). It is also a movement for social justice built on a belief in, and respect for, the rights of people who use drugs.


In the context of drugs or alcohol, withdrawal is when a person cuts out, or cuts back, on using the substance, also known as detoxification or detox. In a context of sexual risk reduction, it refers to the insertive partner in penetrative sex withdrawing before ejaculation. It is not a particularly effective way to lower the risk of HIV transmission or pregnancy.


In everyday language, a general movement upwards or downwards (e.g. every year there are more HIV infections). When discussing statistics, a trend often describes an apparent difference between results that is not statistically significant. 

prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

clinical trial

A research study involving participants, usually to find out how well a new drug or treatment works in people and how safe it is.

The researchers looked at data from 2000 people who use drugs from three prospective cohorts, focusing on those who reported intentionally using cannabis to help control their crack use. They compared how frequently participants reported using crack before, during and after a period of marijuana use.

Between June 2012 and May 2015 they identified 122 participants who said they used cannabis to reduce crack use. About three-quarters were men, the median age was 46 years and a majority resided in Vancouver's Downtown Eastside neighbourhood. Nearly half reported that they used cannabis every day.

In an adjusted analysis, the researchers found that people used crack significantly less often after a period of cannabis use, though crack use did not decrease during the time they were using marijuana.

"A period of intentional cannabis use to reduce crack use was associated with subsequent decreased frequency of crack use," the researchers concluded. "Use of cannabis peaked during intentional use periods, with a decreasing trend afterwards."

Socias and colleagues are now planning a clinical trial to evaluate the effect of cannabis on crack use. Several other studies are underway looking at whether cannabis or isolated cannabinoids can be used to help manage problematic use of opioids, methamphetamine and alcohol.

Heroine-methamphetamine cocktail

In a related presentation, Anna Palmer from the Burnet Institute at Monash University in Melbourne, Australia, presented findings from a study of drug users who mix substances as a harm reduction strategy.

Since the late 2000s there have been increasing reports that people who inject drugs in Melbourne are mixing heroin and crystal methamphetamine in the same injection – a phenomenon dubbed ‘cocktailing’.

Palmer's team conducted 14 in-depth interviews with selected participants from the Melbourne Injecting Drug User Cohort Study to explore reasons why they decided to combine these two drugs.

Participants reported that they engaged in 'cocktailing' regularly – in fact, many reported that they no longer used heroin or methamphetamine alone. The two main reasons given were using the depressant effect of heroin to mitigate some of the harmful effects of crystal methamphetamine, and to prolong the effects of heroin and extend the amount of time before experiencing withdrawal symptoms.

"Participants predominantly reported cocktailing as an indigenous form of harm reduction minimising the most negative consequences of crystal methamphetamine use and prolonging the time before opioid withdrawal," the researchers concluded.

"Cocktailing of heroin and methamphetamine by people who inject drugs is seen largely as a risky practice but [it] may represent a form of harm reduction," Palmer said.

These studies are among several presented at the conference showing that "the way forward to reduce harm may well come from drug users themselves," said Harm Reduction International Executive Director Rick Lines.


Socias ME et al. Intentional use of cannabis to reduce crack cocaine use among people who use drugs in a Canadian setting: a longitudinal analysis. 25th International Harm Reduction Conference, Montréal, abstract 473, 2017.

View the abstract on the conference website.

Palmer A et al. (Higgs P presenting) Methamphetamine and heroin 'cocktail' injecting as harm reduction: qualitative findings from a community-recruited cohort of people who inject drugs in Melbourne, Australia. 25th International Harm Reduction Conference, Montréal, abstract 785, 2017.

View the abstract on the conference website.