A cup of coffee does'nt sober up people with alcohol intoxication, contrary to the popular opinion, says a new study.
The study conducted using mouse model has shown that popular caffeinated "alcohol-energy" drinks don't reverse the negative cognitive impact of alcohol.
"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," said co-author Dr Thomas Gould, of Temple University, in extending the research to what it means for humans.
"People who have consumed only alcohol, who feel tired and intoxicated, may be more likely to acknowledge that they are drunk.
"Conversely, people who have consumed both alcohol and caffeine may feel awake and competent enough to handle potentially harmful situations such as driving while intoxicated or placing themselves in dangerous social situations," he added.
During the study, researchers found that caffeine made mice more alert but did not reverse the learning problems caused by alcohol, including their ability to avoid things they should have known could hurt them.
They gave groups of young adult mice various doses, both separately and together, of caffeine and of ethanol (pure alcohol) at levels known to induce intoxication.
The doses of caffeine were the equivalent of one up to six or eight cups of coffee for humans. Control mice were given saline solution.
Ethanol, as expected, increased locomotion and reduced anxiety and learning in proportion to the dose given.
In other words, intoxicated animals were more relaxed and moved around more but learned significantly less well than control mice to avoid the part of the maze with the unpleasant stimuli.
When the drugs were given together, ethanol blocked caffeine's ability to make the mice more anxious.
Conversely, caffeine did not reverse ethanol's negative effect on learning. As a result, alcohol calmed the caffeine jitters, leaving an animal more relaxed but less able to avoid threats - a combination that the authors speculated could make people more likely to believe they are not drunk or not impaired enough to have problems functioning.
"The alcohol-energy drink combinations have skyrocketed in popularity," Gould said.
He cited other evidence that these drinks produce deficits in general cognitive ability and raise the odds of alcohol-related problems such as drunken-driving citations, sexual misconduct, and needing medical assistance.
The study appears in the journal Behavioural Neuroscience.