Dec. 10, 2009 -- Gulping down coffee won’t sober you up if you’re drunk, but it may make you awake enough to be dangerous, new research suggests.
Researchers draw that conclusion from laboratory experiments on mice, in which caffeine made drunken rodents more alert but didn’t reverse learning problems caused by alcohol.
Their study is published in the journal Behavioral Neuroscience.
“The myth about coffee’s sobering powers is particularly important to debunk because the co-use of caffeine and alcohol could actually lead to poor decisions with disastrous outcomes,” Thomas Gould, PhD, of Temple University and one of the study authors, says in a news release. “People who have consumed only alcohol, who feel tired and intoxicated, may be more likely to acknowledge that they are drunk.”
Gould tells WebMD in an email that "coffee may reduce the sedative effects of alcohol, which could give the false impression that people are not as intoxicated as they really are."
But caffeine’s effect as a stimulant may create the illusion in intoxicated people that they are alert and competent enough “to handle potentially harmful situations, such as driving while intoxicated or placing themselves in dangerous social situations,” Gould says.
He and colleague Danielle Gulick, PhD, now of Dartmouth College, gave groups of young adult mice various doses of alcohol and caffeine by injection prior to learning a maze. A comparison group of mice was given only saline solution.
Alcohol increased movement and reduced anxiety and learning in the mice in proportion to doses given, the researchers say. The drunken mice became more relaxed and moved around more, but learned significantly less than animals given only saline.
The scientists tested three aspects of behavior -- the ability to learn which part of a maze to negotiate in order to avoid exposure to a bright light or sound; anxiety, which was reflected by time spent exploring the maze’s open areas, and general locomotion.
The drunken mice learned significantly less well than the sober ones in trying to avoid the frightening bright light or loud noise.
The doses of caffeine given to the mice were the equivalent of one to six or eight cups of coffee for humans.
When caffeine and alcohol were given together, the alcohol blocked caffeine’s ability to make the mice more anxious, but caffeine failed to reverse the negative effects that alcohol has on learning, according to Gould and Gulick.
The alcohol calmed caffeine-caused jitters in mice, leaving them less able to avoid threats, the authors say. The researchers write that although a combination of caffeine and alcohol consumed by people “may increase alertness during intoxication, and decrease the awareness of intoxication, there may be no equivalent rescue of learning. Thus, drinkers may consumer more alcohol when they are also consuming caffeine.”
“The bottom line is that, despite the appeal of being able to stay up all night and drink, all evidence points to serious risks associated with caffeine-alcohol combinations,” Gould says in the news release.