People are putting their health in danger by mixing energy drinks with alcohol, new research suggests.
Scientists in America questioned 4,271 college students about their alcohol consumption and the problems they have faced.
In a typical session involving energy drinks, they drank up to 36% more than other students, and they also reported twice as many episodes of weekly drunkenness.
Study leader Dr Mary Claire O'Brien, from Wake Forest University Baptist Medical Centre in New Carolina, said: "We knew anecdotally - from speaking with students, and from researching internet blogs and websites - that college students mix energy drinks and alcohol in order to drink more, and to drink longer.
"But we were surprised that the risk of serious and potentially deadly consequences is so much higher for those who mixed energy drinks with alcohol, even when we adjusted for the amount of alcohol."
She added: "Students whose motor skills, visual reaction times, and judgement are impaired by alcohol may not perceive that they are intoxicated as readily when they're also ingesting a stimulant. Only the symptoms of drunkenness are reduced - but not the drunkenness.
"They can't tell if they're drunk; they can't tell if someone else is drunk. So they get hurt, or they hurt someone else."