Over the past 20 years, 23 states and the District of Columbia have
legalized marijuana for medical
use.
Despite these changes to state laws, opponents continue to argue that
marijuana causes more harm than good. A new
study refutes
their claims and shows that marijuana is safer than alcohol and tobacco,
and researchers and policymakers may have overestimated the risks
associated with its use.
Researchers Use Novel Approach to Compare Mortality Risks
Research conducted by Dirk Lachenmeier and Jรผrgen Rehm, and published in
Scientific Reports in January 2015, investigated the mortality risk
associated with seven substances by comparing the lethal dose of each
substance 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 of the substances.
The 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 substances in
alcoholic beverages. Previous attempts to compare the dangers of
substances of abuse were based largely on anecdotal, rather than
scientific, evidence, which meant that policymakers had to rely on
educated guesses and survey data from developed nations 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 of abuse. However, many of these approaches were
based on expert panel judgments on harm indicators, such as intoxication
and physical and psychological dependence.
Evidence for Marijuana’s Safety Grows
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 more deadly 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 did not 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 that the
discrepancy between their mortality risks was this large.
Researchers Call for Changes to Federal Marijuana Laws
Despite their known health risks, alcohol and tobacco are exempted from
the Controlled Substances Act due to cultural and economic reasons.
Alcohol and tobacco have been acceptable substances in U.S. culture
since well before the repeal of Prohibition in 1933, and they are two of
the most widely used
substances
nationally. The researchers believe that the risks of alcohol and
tobacco may have been underestimated in the past, and are urging federal
government to focus their efforts more on mitigating the harmful effects
of alcohol and tobacco than on other substances, such as 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. There
has never been a case of a cannabis overdose death. This lends weight to
the argument that marijuana should be removed from Schedule I of the
Controlled Substances Act, a category reserved for the most dangerous
substances.
