Mixing alcohol with energy drinks may sound harmless enough at first; after all, alcohol is a depressant, so pairing it with a stimulant should even things out, right? Unfortunately, it's not that simple.
Under normal circumstances, most of us begin to feel sluggish or sleepy after a few alcoholic drinks. We can sense that we've had enough (or too much!) to drink, and ideally we'll slow down our consumption as a result. But when you add energy drinks to the mix, the stimulant effects of caffeine, plant-based ingredients, or sugars in the drink can mask the effect of the alcohol, making us feel more sober and alert than we really are. The energy drinks prevent drinkers from feeling the effects of alcohol, but they do not reduce alcohol concentrations or improve the body's ability to metabolize alcohol [sources: CDC, Ferreira].
A study at Australian National University found that men and women aged 18-30-years-old who drank alcohol combined with energy drinks had a stronger desire to keep drinking than study participants who drank alcohol on its own [source: McKetin and Miller]. Taking it a step further, a study in a college bar district in Gainesville, Florida, found that bar patrons who drank alcohol mixed with energy drinks were three times more likely than drinkers of alcoholic beverages alone to leave the bar with a breath alcohol content (BrAC) of .08 or greater and had a four times greater risk of intending to drive after leaving the bar [source: Thombs et al.].