A comprehensive review of the effects of mixing caffeinated energy drinks with alcohol

Background In response to concern about whether mixing caffeinated energy drinks with alcohol (AED) increases alcohol consumption and related harm, and the role of industry in this debate, we conducted a comprehensive review of the research evidence on the effects of AED and documented industry involvement in this research. Method A systematic review of 6 databases. Studies must have examined the effect of consuming alcohol with energy drinks (ED) or caffeine on alcohol-related outcomes. Results 62 studies were identified; 29 were experiments, 9 had industry ties (8 with Red Bull GmbH). Young adults who consumed AED drank more alcohol and experienced more alcohol-related harm than other drinkers. There was insufficient evidence to conclude that AED led to increased alcohol consumption or altered the nature of alcohol-related harm. However, AED consumers reported that AED increased stimulation and alertness, offset fatigue from drinking, and facilitated drinking. Experimental research also found that combining ED or caffeine with alcohol increased stimulation and alertness, offset alcohol-related fatigue and increased the desire to keep drinking. It did not change BAC, perceived intoxication, perceived impairment and it did not reverse alcohol-induced impairment on simple psychomotor tasks. Combining ED/caffeine with alcohol reduced alcohol-induced impairment on some but not all aspects of complex tasks. Although few in number, studies with industry ties presented contrary evidence. Conclusion A growing body of evidence suggests that AED may facilitate drinking and related harms via its effects on intoxication but a causal link needs to be confirmed. The influence of industry involvement in this area of research needs to be monitored.