It appears that young adults’ interest in marijuana may wane once they gain access to alcohol. A recent study from the University of Illinois measured alcohol and marijuana use in people between the ages of 18 and 24. They found a dramatic increase in alcohol use with newly 21-year olds – understandable since they could now buy it legally. However researchers were surprised that at the same time, after users’ 21st birthdays, there was a sudden decrease in marijuana use. The change was found to be more dramatic in women than men.
“Alcohol appears to be a substitute for marijuana. This sudden decrease in the use of marijuana is because they suddenly have easy access to alcohol,” U of I researcher Ben Crost said. He said that all the costs and benefits from policies designed to reduce alcohol consumption must be weighed in light of these findings.
“We need to take this possible substitution behavior into account,” Crost said. “Marginally lowering the minimum legal drinking age would decrease the probability of marijuana consumption in young adults by about 10 percent. So, policies aimed at restricting alcohol consumption among young adults are likely to have the unintended consequence of increasing the use of illegal drugs, such as marijuana.
“If you think alcohol is much more harmful to people’s health, then you should probably restrict alcohol use. If you think marijuana is more harmful, then you might want to consider loosening the restrictions for alcohol,” he said. The study, co-authored by Santiago Guerrero, was published in the Journal of Health Economics.
This article appears in Jul 9-15, 2015.
