"Though a lot of people are familiar with drinking a caffeinated beverage or an alcoholic beverage, few of them are familiar with drinking the combination," said Dr. Matthew Davis, associate professor of pediatrics and communicable diseases and an associate professor of public policy at the Ford School of Public Policy at the University of Michigan in Ann Arbor. "That combination is up to five beers at once in a single serving of a caffeinated alcoholic beverage and about the equivalent of one cup of coffee in terms of caffeine."
Many young adults drink caffeinated alcoholic beverages because they create a desirable feeling.
"They experience a high degree of intoxication due to alcohol and the caffeine has an effect that seems to override the intoxicating effects of alcohol. It's called 'wide awake drunk,'" said Bruce Goldberger, professor and director of toxicology at the University of Florida College of Medicine in Gainesville.
According to Goldberger, studies have shown that drinking caffeinated alcoholic beverages raises a person's blood alcohol concentration and also makes someone more likely to engage in risky behavior, such as driving while impaired.
"The amount of alcohol in a 23-ounce can is sufficient to produce a blood alcohol concentration above the statutory limit in all 50 states," Goldberger said.
A new study also highlights the dangers of mixing alcohol and caffeine. Researchers led by Amelia Arria, director of the Center for Young Adult Health and Development at the University of Maryland School of Public Health found that fourth-year college students who consumed energy drinks on a daily or weekly basis were at higher risk for alcohol dependence compared to their peers who drank them less frequently. The researchers kept other risk factors for alcohol dependence -- such as family history, age and behavior problems in childhood -- constant throughout the study.
"The association between energy drinks and alcohol dependence persisted even after we controlled for other risk factors," said Arria.
Arria also said the study did not look into why this association existed, and she said more research needs to be done to examine the relationship further. She added that this research drives home an important point.
"It underscores the potential public health risk of combining alcohol and energy drinks. It supports the fact that people who drink energy drinks are likely to mix them with alcohol, and that's likely to increase the risk for alcohol dependence," she said.
People need to know that there is a difference between drinks such as Kahlua and Coke, and pre-mixed alcohol and caffeine-containing drinks such as Four Loko and Joose.
"We haven't seen the level of problems associated with these other drinks as we have with the pre-mixed ones," said Arria.
"Those people who don't get it, and who don't understand the connection, may be more inclined to try these things for the first time because they're already combined," said Jeffrey Parsons, professor of psychology at Hunter College in New York.
Those problems have been well-publicized, such as the incident involving nine Central Washington University students who drank Four Loko and had to be rushed to the hospital.