Vodka Red Bull is an alcoholic beverage consisting of energy drink Red Bull and varying amounts of vodka. It is popular among 18- to 30-year olds in bars and nightclubs around the world. Red Bull has been used as mixer in Europe since the 1990s, but the drink became especially popular in North America in the 21st century. The ratio of Red Bull to Vodka varies but is usually 3/4 of Red Bull and 1/4 of Vodka. In some places it is customary to serve an entire can with a single shot of vodka; in others, a can may be split between several glasses, each containing several shots of vodka. The Red Bull dominates so that the flavour of the alcohol is not too strong. Caffeinated alcoholic energy drinks can be hazardous as caffeine can mask the influence of alcohol and may lead a person to misinterpret their actual level of intoxication. However, in 2012 the scientific review paper "Energy drinks mixed with alcohol:misconception, myths and facts" was published. This review discusses the available scientific evidence on the effects of mixing energy drinks with alcohol. The authors note that excessive and irresponsible consumption of alcoholic drinks has adverse effects on human health and behaviour, but it should be clear that this is due to the alcohol, and not the mixer. They concluded that there is no consistent evidence that energy drinks alter the perceived level of intoxication of people who mix energy drinks with alcohol and found no evidence that co-consumption of energy drinks causes increased alcohol consumption.