University of Washington
Does legal marijuana tempt pot users to consume more alcohol -- or are they likely to opt for cannabis instead of chardonnay?
A University of Washington team of researchers sought to address
those questions in the context of evolving marijuana policies in the United
States. Their findings, published online Dec. 21 in the journal Alcoholism:
Clinical & Experimental Research, highlight the difficulties of gauging
the impact of a formerly illicit drug as it moves into the mainstream.
Recreational marijuana use is now legal in four states and
medical marijuana in 23 states. Research on legalization policies has focused
largely on how they impact marijuana access and use. But the UW team wanted to
know how legalization affects the use of alcohol, by far the nation's most
popular drug.
The majority of adults in the U.S. imbibe to varying degrees,
and alcohol abuse is the third leading preventable cause of death nationwide.
Drinking accounts for almost one-third of driving fatalities annually, and
excessive alcohol use cost $223.5 billion in 2006 alone.
"We chose to focus on alcohol because even relatively small changes in alcohol consumption could have profound implications for public health, safety and related costs," said lead author Katarína Guttmannová, a researcher in the UW's Social Development Research Group.
The researchers sought to determine whether legalizing marijuana
led to it becoming a substitute for alcohol or tended to increase consumption
of both substances. If it was the former, they reasoned, that could greatly
reduce the costs of healthcare, traffic accidents and lower workplace
productivity related to excessive drinking.
But if legalized marijuana resulted in increased use of both
drugs, costs to society could increase dramatically, particularly since those
who use both substances tend to use them at the same time.
Those who use both
substances simultaneously are twice as likely to drive drunk and face social
troubles such as drunken brawls and relationship problems, a recent study
found.
Drawing on previous studies, the researchers hypothesized that
legalization of marijuana could result in either substitution or complementary
effects.
Marijuana and alcohol both provide users with similar "reward and
sedation" effects, the researchers noted, which could prompt users to
substitute one for the other.
But blood levels of THC, the chemical responsible
for most of marijuana's pleasurable psychological effects, increase with
simultaneous alcohol use -- so the quest for a better high might lead people to
use both substances.
The researchers reviewed more than 750 studies on marijuana and
alcohol use and focused on 15 that specifically addressed the links between
marijuana policies and drinking. They looked at how decriminalized marijuana,
medical marijuana and recreational marijuana impacted alcohol use.
The findings of those studies fluctuated widely, depending on
the demographic and the type and frequency of alcohol and marijuana use. One
study, for example, found that states where marijuana is decriminalized had
more emergency room visits related to marijuana and fewer visits linked to
alcohol and other drugs.
Some studies found that high school seniors in states
where pot was decriminalized tended to drink less, while other research found
that college students who used pot also drank more.
Findings around medical marijuana also varied. One study
reported that states with medical marijuana dispensaries had higher rates of
both marijuana and alcohol use, as well as higher admissions into alcohol
treatment facilities. But while states with medical marijuana had fewer
alcohol-related fatalities overall, those with dispensaries saw more of those
deaths.
Other research found that while legalized medical marijuana
wasn't associated with any increases in underage drinking, it was linked with
more binge drinking and simultaneous use of pot and alcohol among adults.
The issue is particularly complicated in Washington state, which
legalized recreational marijuana use in 2012 after privatizing liquor sales the
previous year. As a result, the uptick in alcohol sales made it difficult to
isolate the impacts of legalized marijuana on drinking from the change in
alcohol policy.
The researchers concluded that there's evidence of marijuana and
alcohol being both substitutes and complements. Given the rapidly evolving
landscape of marijuana policy, they say further study will be important to
understand how changes in marijuana laws impact the use of alcohol and other
drugs.
In particular, Guttmannová said, future studies should address
specific dimensions of marijuana policies, timing of policy change and
implementation, and different aspects of marijuana and alcohol use, such as age
of users and whether they are episodic or regular consumers.
"This is a complicated issue and requires a nuanced
approach," she said. "We were hoping to have more clear-cut answers
at the end of our research. But you know what? This is the science of human
behavior, and it's messy, and that's OK."