"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.
As a result of this and other incidents, four states and a number of college campuses have banned the sale of alcoholic energy drinks. In New York, the State Liquor Authority and some of the largest beer distributors agreed to stop selling these drinks throughout the state.
Other experts think a ban could be counterproductive.
"I'm concerned that we're about to do for young people exactly what we've learned not to do," said Parsons. "The more we stigmatize something and make an issue out of it, the more attractive it's going to be."
He thinks there needs to be a much greater emphasis on how to prevent young people from picking up one of these drinks.
"I think we need, rather than just focusing on 'let's ban these products,' we need more research and prevention-based efforts to deal with the public health needs."