Canada was the first country to legalize medical marijuana way back in 2001, and recreational cannabis is set to become legal in 2018. Despite these changes to federal laws, opponents continue to argue that marijuana causes more harm than good. But a research study conducted in Europe shows that marijuana is safer than alcohol and tobacco, and that researchers and policymakers may have overestimated the risks associated with cannabis use.
Researchers use the MOE Approach to Compare Mortality Risks
This research—conducted by Dirk Lachenmeier and Jürgen Rehm, and published in Scientific Reports in January 2015—investigated the mortality risk associated with seven substances. They did this by comparing the lethal dose of each item with the typical amount used. This ratio, referred to as the margin of exposure (MOE), was used to determine the risk of dying from an overdose of each drug.
MOE is a novel method for comparing the mortality risk of different substances. Introduced by the European Food Safety Authority in 2005 as an approach for assessing the risk of toxic compounds, it had only ever been used in the addiction field for evaluating components of alcoholic beverages.
Previous attempts to compare the dangers of other potentially addictive items were based largely on anecdotal, rather than scientific evidence. This meant that policymakers had to rely on educated guesses and survey data when making legislative decisions. Only in the past decade have researchers begun to use robust scientific techniques to classify the mortality risks of particular substances. However, many of these approaches were based on expert panel judgments on harm indicators, such as intoxication and physical and psychological dependence.
Alcohol 114 Times Deadlier Than Cannabis
Lachenmeier and Rehm's research revealed that, of all the substances analyzed, alcohol posed the highest mortality risk at an individual level, followed by heroin, cocaine, tobacco, ecstasy, methamphetamine and marijuana. Alcohol was found to be about 114 times deadlier than marijuana, which was the only substance that was classified as having a low mortality risk.
The researchers' classifications were based solely on the substances themselves and didn’t take into account environmental risk factors, such as the sharing of contaminated needles by intravenous drug users.
Previous studies, including a comparison of the toxicity of commonly abused substances published in the journal Addiction in June 2004, ranked marijuana as safer than alcohol and tobacco, but it was not known then that the discrepancy between their mortality risks was this large.
Researchers Call for Changes to Marijuana Laws
The researchers believe that the risks of alcohol and tobacco may have been underestimated in the past, and are urging governments to focus their efforts more on mitigating the harmful effects of alcohol and tobacco, rather than other substances like marijuana.
In contrast, the risks of marijuana may have been overestimated. For the mortality endpoint alone, the findings showed marijuana's MOE to be above safety thresholds at the individual and population levels. It’s also worth remembering that there has never been a case of death by cannabis overdose.