As the legalization of medical marijuana and marijuana use are both on the rise in the United States, people are not necessarily using alcohol less and may be unaware of the risks of combining alcohol and marijuana, according to researchers.

A new study from Penn State found that compared to people who only drank alcohol, those who used alcohol and marijuana simultaneously were more likely to drink heavier and more often. They were also more likely to experience alcohol-related problems — like impulsive actions they later regretted.

“The results suggest that individuals who simultaneously use alcohol and marijuana are at a disproportionately higher risk for heavy, frequent, and problematic substance use,” said Ashley Linden-Carmichael, assistant research professor at the Edna Bennett Pierce Prevention Research Center at Penn State.

The researchers said the findings — recently published in the journal Substance Use and Misuse — also suggest that prevention and intervention programs should take into account not just alcohol, but also if people are using additional substances, as well.

“Right now, a lot of campus programs focus on whether students are drinking, and while sometimes they are asked about other substances, it’s not necessarily whether they’re using these substances simultaneously,” Linden-Carmichael said.
“I think we do need to be asking about whether they’re drinking in combination with other drugs and educating students about how that exacerbates their risk.”
According to the researchers, marijuana use is at an all-time high among young adults in the U.S., possibly leading to people using marijuana and alcohol simultaneously.

“The problem with simultaneous use is that it can affect people cognitively and perceptually, and also have an impact on motor impairment,” Linden-Carmichael said. “There is a burgeoning area of research that is examining why people are using marijuana and alcohol together and what those effects are.”

In the study, Linden-Carmichael said she and the other researchers were interested in learning more about how people use marijuana and alcohol together. They also wanted to explore whether personality traits — like the tendency to pursue new and exciting experiences, or “sensation seeking” — were associated with higher odds of using alcohol and marijuana at the same time.

The researchers recruited 1,017 participants from 49 states in the U.S. between the ages of 18 and 25 for the study. The participants provided information about how often they used alcohol, marijuana and the two substances simultaneously. They also filled out questionnaires that measured their experiences with alcohol-related problems, whether they had a sensation-seeking personality, and how they perceived the drinking habits of their friends.

Linden-Carmichael said that across the board, individuals who used alcohol and marijuana simultaneously were at a greater risk than individuals using alcohol alone.

“Even after controlling for the number of drinks a person typically consumed, people who used alcohol and marijuana at the same time were at a greater risk for problems like blacking out, getting in an argument, or other concerns,” Linden-Carmichael said. “Additionally, 70 percent of those who engaged in simultaneous use reported using at least weekly.”

This shows a brain

According to the researchers, marijuana use is at an all-time high among young adults in the U.S., possibly leading to people using marijuana and alcohol simultaneously. The image is in the public domain.

The researchers found that among people who used alcohol and marijuana simultaneously, those who used more frequently were more likely to drink more alcohol, more often, and for longer periods of time. They were also associated with using more marijuana more often.

Additionally, they found that people who used alcohol and marijuana together were more likely to have higher levels of sensation-seeking characteristics and think their friends were drinking larger amounts of alcohol.

Amy L. Stamates, Old Dominion University, and Cathy Lau-Barraco, Old Dominion University, also participated in this work.

Funding: The National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism helped support this research.

About this neuroscience research article

Penn State
Media Contacts:
Katie Bohn – Penn State
Image Source:
The image is in the public domain.

Original Research: Closed access
“Simultaneous Use of Alcohol and Marijuana: Patterns and Individual Differences”. Ashley N. Linden-Carmichael, Amy L. Stamates & Cathy Lau-Barraco.
Substance Use & Misuse. doi:10.1080/10826084.2019.1638407


Simultaneous Use of Alcohol and Marijuana: Patterns and Individual Differences

Background: Simultaneous alcohol and marijuana (SAM) use, or using alcohol and marijuana in such a way that their effects overlap, is associated with negative health and behavioral outcomes. Objectives: Our study sought to fill gaps in our knowledge on this emerging public health concern by comparing SAM users and alcohol-only users on individual-level factors and substance use outcomes as well as examining associations of SAM use frequency, within users.

Methods: Participants were recruited through online postings. Our analytic sample consisted of 1017 young adults (18–25 years) who reported past-month alcohol use. Most were male (67.8%), Caucasian (71.5%), and had attended at least some college (74.8%).

Results: Past-year SAM users reported higher levels of sensation seeking and greater perceptions of their close friends’ drinking behavior in comparison to alcohol-only users. SAM users reported heavier and more frequent alcohol use than alcohol-only users. Within past-year SAM users, 70% reported SAM use at least weekly. More frequent SAM use was associated with all alcohol use outcomes (e.g., weekly quantity, frequency, alcohol-related problems) and marijuana use outcomes (e.g., quantity, frequency, peak use) and higher drinking norms.

Conclusions/Importance: It is clear that SAM users are a vulnerable sub-population of young adult drinkers. SAM users are differentiated from alcohol-only users in terms of their personality characteristics and perceptions of peer groups’ drinking. SAM users and more frequent users are also at heightened risk for substance use outcomes. Prevention and intervention efforts targeting high-risk drinking may benefit from also assessing whether they simultaneously use alcohol and marijuana.

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