Young adults who mix alcohol with caffeinated drinks are more likely to engage in risky sexual behaviours than those who avoid energy drink cocktails, according to new research.
Researchers from the University of Buffalo in New York surveyed 648 students aged between 18 and 21. They were asked how many times they had consumed alcohol mixed with an energy drink in the past month and whether they'd engaged in a risky sexual activity.
The results showed a third of students had drank caffeine with alcohol and those students were more likely to have casual sex with someone they weren't in love with, weren't exclusive with or didn't know very well.
They were also more likely to have been drunk or high when they had sex.
However, mixing caffeine and alcohol did not appear to impact whether they used protection or not.
The results were the same for both men and women.
When study author Kathleen Miller compared the behaviour of the students when they had alcohol without caffeine, she found they were much more rational, which led her to conclude that the addition of caffeine had effects on their promiscuity that didn't happen with alcohol alone.
"The consequences of hooking up drunk aren't limited just to unintended pregnancy or STDs; they can also include sexual victimisation, post-sexual-encounter regret and social stigmatisation, particularly for women," Miller told BuzzFeed.
"Those risks are higher if you don't know your partner and his/her sexual history very well, and they're higher if you're drunk, because you're more likely to miss the often-subtle cues that tell you this encounter is a bad idea."
She said the reasons for the boost in risky behaviour are quite obvious.
"When you're drinking lots of alcohol, your judgment is impaired, and if you're having caffeine, you don't realise how impaired you are," she said.
According to the Foundation for Alcohol Research and Education, the amount of caffeine in some energy drinks exceeds 500mg — the same as six cups of coffee.
Caffeine masks the depressant effects of alcohol so you're less likely to feel intoxicated and more likely to drink more.
Amy Pennay, a researcher at the Turning Point Alcohol and Drug Centre in Melbourne, says researchers are aware that people who drink alcohol and energy drinks engage in more risky behaviour. However what's not known is whether it's because natural risk-takers are attracted to drinking caffeinated drinks and alcohol, or whether it's the drinks that are causing ordinary people to take big risks.
"It's not conclusive – some of the literature says when people consume alcohol and energy drinks they engage in more risks," she said.
"What is really unclear is whether it is just people who are really attracted to drinking alcohol and energy drinks who are more risk-takers in life."
Pennay said more research will be done in the coming years.
"What we really need is some experimental data to give people in a laboratory setting alcohol and energy drinks and see if they engage in risk-taking behaviour," she said.
But regardless of the findings, Pennay said no one should drink more than two energy drinks in one day.
"Drinking too much caffeine can increase your heart-rate, give you heart palpitations and give you anxiety," she said.
"Energy drinks are marketed really well – they're exciting and cool. Young people between 16 and 20 are really attracted to that. We probably do need to match that popular marketing with some caution. I wish there was a more equal balance in public health messages."
The study was published in the Journal of Caffeine Research.